API INTEGRATIONS · API 連携

Japanese businesses selling on Rakuten, Amazon Japan, and Yahoo Shopping managing three separate seller portals, three separate inventory sheets, and three separate order processing workflows are building the same inefficiency three times. An API integration layer handles all three channels from one system.

Ignited Nepal plans and builds API integrations for Japanese businesses: from unified e-commerce channel management across Rakuten, Amazon Japan, and Yahoo Shopping to kintone-accounting connections, Japan Post tracking integration, and Japanese character encoding handling.

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Who This Is For

Japanese retailers selling on multiple domestic e-commerce platforms face an inventory synchronisation and order routing challenge that grows more severe with each additional channel. A single product sold simultaneously on Rakuten and Amazon Japan can result in an oversell if the inventory count in one portal is not updated within seconds of a sale on the other. Manual inventory management across three portals is not a viable long-term operational model for any business above a small order volume. A unified inventory management system connected to all three platforms via API prevents overselling and reduces the per-order processing time across all channels.

kintone is a widely adopted low-code business application platform in Japan, used by many small and medium-sized businesses for project management, customer data, and operational workflows. kintone's REST API allows its data to be connected to external systems including freee and Yayoi accounting software, external databases, and notification services. Businesses that manage customer and project data in kintone and accounting data in freee or Yayoi are commonly re-entering data between the two systems manually, a step that the kintone REST API makes unnecessary.

Japanese retail businesses with a physical store and an online presence manage the challenge of keeping in-store and online inventory in sync. When a product sells in the physical store, the inventory count on the Rakuten or EC-Cube online store needs to update immediately to prevent an online order being placed for a product no longer in stock. A POS-to-e-commerce API integration handles this update automatically with each in-store transaction.

Japanese logistics businesses and e-commerce operators that ship via Japan Post, Yamato Transport, and Sagawa Express can provide customers with real-time shipment tracking by embedding the carrier tracking APIs into their own customer-facing platform. A customer who can track their parcel from within the retailer's order history page or LINE notification does not need to navigate to the carrier's website. This improves the post-purchase experience and reduces the volume of customer service enquiries about order status.

/ What's broken

What's Broken

Three e-commerce platforms managed with three separate logins and no unified inventory

Japanese retailers selling on Rakuten, Amazon Japan, and Yahoo Shopping without a unified inventory management system are managing their most operationally critical metric, how much stock is available, in three separate places with no synchronisation between them. When a product sells on Rakuten, the Amazon Japan and Yahoo Shopping inventory counts for that product do not update automatically. If all three portals show 10 units available and the product sells 10 units on Rakuten, the Amazon Japan and Yahoo Shopping listings still show 10 units, and any orders placed for those units will oversell. The only protection against this in a manual system is frequent manual updates across all three portals, a process that is both time-consuming and inherently error-prone. An API integration connecting a central inventory management system to all three platforms updates all channels simultaneously with each sale.

Japanese character encoding errors in API integration

Any API integration handling Japanese business names, product names, customer addresses, or transaction descriptions must correctly handle Japanese character sets: kanji, hiragana, katakana, and full-width alphanumeric characters. When an integration built on a Western API platform does not explicitly configure UTF-8 encoding throughout the data pipeline, Japanese characters arrive at the destination system as corrupted strings or question marks. This encoding failure is not visible during basic integration testing unless the test data includes actual Japanese characters. The fix is explicit UTF-8 encoding specification at every point in the data pipeline where Japanese text is present: in the API request headers, in the data transformation logic, in the database storage configuration, and in the output display. Every API integration handling Japanese data must be built with this as a confirmed requirement, not an assumed default.

kintone data not connected to accounting

Japanese businesses using kintone for customer management, project tracking, or sales pipeline data and freee or Yayoi for accounting are maintaining two parallel records of their business activity that share no data automatically. When a project is completed in kintone, the associated invoice should be created in freee or Yayoi automatically. When a customer record is updated in kintone, the corresponding record in the accounting system should reflect the change. kintone's REST API supports both reading from and writing to kintone records. freee and Yayoi both provide APIs for invoice and transaction creation. The integration between them is straightforward in principle and eliminates a significant volume of manual data re-entry for businesses managing a high number of projects or invoices.

Japan Post and Yamato tracking not embedded in the customer experience

Japanese e-commerce businesses that send tracking numbers to customers via email, as a number the customer needs to copy and paste into the Japan Post or Yamato website, are providing a post-purchase experience that creates unnecessary friction. Japan Post provides a parcel tracking API that returns current shipment status for a given tracking number. Yamato's B2 Cloud service provides equivalent tracking data via API. Embedding the tracking status directly in the order confirmation email, the order history page on the retailer's website, or a LINE notification means the customer does not need to navigate to the carrier's website. The API calls are simple GET requests with the tracking number as a parameter, returning a status code and estimated delivery information that can be displayed in whatever format the retailer's platform uses.

/ What we engineer

What We Do

API integration diagnostic for Japanese businesses

We begin with an API integration diagnostic for Japanese businesses that maps the data flows between the existing business systems, identifies every manual data transfer step, and assesses the API capabilities of each platform in the current stack. For Japanese e-commerce businesses, the diagnostic almost always identifies the multi-channel inventory synchronisation gap and the Japan Post or Yamato tracking embedding opportunity as high-priority items.

Multi-channel e-commerce integration

For multi-channel e-commerce integration, we design and build the connection between the central inventory management system and the Rakuten, Amazon Japan, and Yahoo Shopping seller APIs. The integration handles real-time inventory decrement across all channels with each sale, order data routing from all three channels into the central order management system, and status updates returned to each channel (shipped, cancelled, refunded) from the central system. We configure the Japanese character encoding throughout the data pipeline and test with actual Japanese product names and customer addresses before go-live.

kintone integrations

For kintone integrations, we build the connection between kintone and the accounting system using kintone's REST API and the freee or Yayoi API. The typical integration creates invoices in the accounting system when a kintone project record reaches a completion status, syncs customer data between kintone and the accounting system, and updates kintone records with payment status received from the accounting system. We handle Japanese character encoding at every point in this integration.

Logistics tracking integration

For logistics tracking integration, we connect the Japan Post and Yamato tracking APIs to the retailer's order management platform or LINE notification system. Each shipment's tracking number, retrieved from the carrier API, is embedded in the post-dispatch notification sent to the customer. The integration polls the carrier API at set intervals for updates during the delivery window and sends an automated notification when the package is delivered.

POS-to-e-commerce integration

For POS-to-e-commerce integration, we connect the POS system's inventory update event to the Rakuten or EC-Cube API, ensuring that each in-store sale decrements the online inventory count in real time.

Documentation and handover

We document all integrations with full Japanese-language notes where the business requires it, and ensure that the configuration and error handling logic is understood by the business's internal team on handover.

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/ What changes

What Changes

Before

After

BeforeJapanese retailers selling on Rakuten, Amazon Japan, and Yahoo Shopping without a unified inventory management system are managing their most operationally critical metric, how much stock is available, in three separate places with no synchronisation between them. When a product sells on Rakuten, the Amazon Japan and Yahoo Shopping inventory counts for that product do not update automatically. If all three portals show 10 units available and the product sells 10 units on Rakuten, the Amazon Japan and Yahoo Shopping listings still show 10 units, and any orders placed for those units will oversell. The only protection against this in a manual system is frequent manual updates across all three portals, a process that is both time-consuming and inherently error-prone. An API integration connecting a central inventory management system to all three platforms updates all channels simultaneously with each sale.

AfterOverselling across multi-channel inventory is eliminated. When all three e-commerce channels are connected to a central inventory system with real-time synchronisation, inventory counts across Rakuten, Amazon Japan, and Yahoo Shopping update simultaneously with every sale. Oversells stop because the inventory source of truth is a single system, not three independent portals.

BeforeAny API integration handling Japanese business names, product names, customer addresses, or transaction descriptions must correctly handle Japanese character sets: kanji, hiragana, katakana, and full-width alphanumeric characters. When an integration built on a Western API platform does not explicitly configure UTF-8 encoding throughout the data pipeline, Japanese characters arrive at the destination system as corrupted strings or question marks. This encoding failure is not visible during basic integration testing unless the test data includes actual Japanese characters. The fix is explicit UTF-8 encoding specification at every point in the data pipeline where Japanese text is present: in the API request headers, in the data transformation logic, in the database storage configuration, and in the output display. Every API integration handling Japanese data must be built with this as a confirmed requirement, not an assumed default.

AfterOrder processing moves to a single workflow. Orders from all three channels appear in one order management system. A staff member processing orders works from one queue rather than three separate seller portals. The processing time per order decreases and the risk of a channel being neglected during a busy period is removed.

BeforeJapanese businesses using kintone for customer management, project tracking, or sales pipeline data and freee or Yayoi for accounting are maintaining two parallel records of their business activity that share no data automatically. When a project is completed in kintone, the associated invoice should be created in freee or Yayoi automatically. When a customer record is updated in kintone, the corresponding record in the accounting system should reflect the change. kintone's REST API supports both reading from and writing to kintone records. freee and Yayoi both provide APIs for invoice and transaction creation. The integration between them is straightforward in principle and eliminates a significant volume of manual data re-entry for businesses managing a high number of projects or invoices.

AfterJapanese character encoding errors are prevented from the build stage. When UTF-8 encoding is specified throughout the data pipeline before the integration is deployed, Japanese product names and customer addresses arrive at the destination system correctly. The encoding failures that corrupt Japanese text in Western API platforms are prevented by design rather than discovered after go-live.

BeforeJapanese e-commerce businesses that send tracking numbers to customers via email, as a number the customer needs to copy and paste into the Japan Post or Yamato website, are providing a post-purchase experience that creates unnecessary friction. Japan Post provides a parcel tracking API that returns current shipment status for a given tracking number. Yamato's B2 Cloud service provides equivalent tracking data via API. Embedding the tracking status directly in the order confirmation email, the order history page on the retailer's website, or a LINE notification means the customer does not need to navigate to the carrier's website. The API calls are simple GET requests with the tracking number as a parameter, returning a status code and estimated delivery information that can be displayed in whatever format the retailer's platform uses.

Afterkintone project completions create accounting invoices automatically. When the kintone-to-accounting integration is live, completing a project in kintone triggers invoice creation in freee or Yayoi without anyone needing to switch systems. The manual re-entry step between project management and accounting is removed.

/ How it works

Process

API Integration Diagnostic

We review the existing systems, the data flows between them, the API capabilities of each platform, and the manual steps currently bridging the gaps. We produce a prioritised integration map with notes on Japanese character encoding requirements for each connection.
Integration Architecture Design

We design the data flow for each integration: the trigger, the data transformation, the destination, the error handling, and the monitoring approach. For multi-channel e-commerce, we design the inventory synchronisation logic and the order routing rules. We confirm the architecture before building.
Character Encoding Configuration

Before writing any integration code, we specify UTF-8 encoding at every layer of the data pipeline that will handle Japanese characters: API request headers, transformation logic, database schemas, and output display. We include Japanese character test data in all test cases.
Integration Build

We build each integration according to the agreed architecture. For kintone integrations, we use kintone's REST API with the correct authentication and field mapping. For e-commerce channel integrations, we connect to Rakuten's RMS API, Amazon Japan's SP-API, and Yahoo Shopping's API with appropriate rate limiting and retry logic for each platform's specific constraints.
Testing with Japanese Data

We test every integration with real Japanese character data: product names in kanji, customer addresses with prefecture and ward characters, and business names in katakana. We confirm that data arrives at the destination system correctly encoded and displayed before connecting to live systems.
Monitoring Setup and Handover

We configure error alerting and performance monitoring for each integration. We document the complete integration architecture in Japanese and English and provide handover training for the business's team.

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/ Common questions

FAQ

Straight answers on scope, timelines and cost. Anything else, ask us directly.

Ask us directly

How do I build a unified inventory management system connected to Rakuten, Amazon Japan, and Yahoo Shopping via API?

Unified inventory management across Rakuten, Amazon Japan, and Yahoo Shopping requires a central inventory management system (either a purpose-built multi-channel management platform such as Sellercloud, SkuVault, or a Japanese-market tool such as Zaiko Robot or Tempostar) connected to each platform's API. Rakuten provides the RMS (Rakuten Merchant Server) API for inventory and order management. Amazon Japan uses the same SP-API (Selling Partner API) as Amazon's other marketplaces. Yahoo Shopping provides its Merchant API for inventory and order handling. The central system receives inventory updates from all channels, decrements the shared inventory count with each sale, and pushes the updated count back to all connected channels. The build requires API authentication setup for each platform, inventory synchronisation logic, and order routing configuration.

How do I handle Japanese character encoding (UTF-8 and shift-JIS) correctly in an API integration?

Japanese character encoding handling starts with establishing UTF-8 as the encoding standard throughout the entire data pipeline. Specify `Content-Type: application/json; charset=UTF-8` in all API request headers. Ensure the database or data store used in the integration is configured to use UTF-8 collation. When consuming data from older Japanese systems that use Shift-JIS encoding, convert the Shift-JIS input to UTF-8 at the point of ingestion using a character set conversion library before passing the data to any subsequent system. Test every point in the pipeline with Japanese test strings containing kanji, hiragana, katakana, and full-width characters before connecting to live data. Encoding errors found after go-live with real customer data are significantly more costly to resolve than encoding errors found during testing.

How do I connect kintone to freee or Yayoi accounting software using the kintone REST API?

kintone's REST API uses JSON and OAuth authentication and allows reading and writing of record data in any kintone application. The integration between kintone and freee is built by configuring a trigger, typically a record status change in a kintone sales or project app, that initiates an API call to freee's invoicing endpoint to create an invoice with the fields from the kintone record (customer name, amount, line items, due date). freee provides a documented REST API for invoice creation. Yayoi provides an API through its Yayoi Online platform for transaction and invoice management. The integration middleware (Make or a custom script) handles the trigger detection, the field mapping between kintone and the accounting system, and the error handling for failed API calls.

How do I embed Japan Post or Yamato tracking into a customer-facing order tracking page using their APIs?

Japan Post provides a parcel tracking inquiry API through its business services portal that accepts a tracking number and returns the current status of the shipment. Yamato Transport's B2 Cloud service provides an equivalent API for business accounts. To embed tracking status in a customer-facing page, the retailer's order management system stores the tracking number at the time of dispatch, and the customer-facing tracking page makes an API call to the carrier API with that tracking number when the customer views their order status. The API response is parsed and displayed in the retailer's own format, typically as a status message and estimated delivery date. For LINE notification integration, the same API call can be triggered by a scheduled check and a LINE message sent to the customer when the status changes to "out for delivery" or "delivered."

How do I integrate PayPay or LINE Pay into a Japanese e-commerce or booking system?

PayPay provides a merchant API that supports QR code payment, online checkout integration, and refund handling. Integration requires a PayPay merchant account, which is available to businesses registered in Japan. The PayPay API uses OAuth 2.0 authentication and provides SDKs for web and mobile payment flows. LINE Pay provides its own merchant API for online payment integration with a connection to the LINE messaging ecosystem, making it a strong option for businesses that also use LINE for customer communication. Both payment gateways require the API payload to handle Japanese yen amounts as integers (no decimal places), Japanese billing addresses, and the correct merchant category codes. For booking systems, both PayPay and LINE Pay can be integrated at the checkout step to process deposits or full payment at the time of booking.

/ Our team

The people behind the work.

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Closing CTA

Japanese businesses managing multi-channel e-commerce, kintone-based operations, and logistics across Japan Post and Yamato are carrying manual data handling overhead at every point where their systems do not connect. The API integrations that remove this overhead are buildable using the documented APIs of each platform. The technical challenges specific to the Japanese market, including character encoding, domestic payment gateway integration, and multi-channel inventory synchronisation, are solvable when they are specified correctly from the design stage. Ignited Nepal runs an API Integration Diagnostic that maps every manual data transfer in the current system setup and produces a prioritised plan for automating each one. The diagnostic is where the work begins.