Japanese Shopify app development solves the problems that no Western Shopify app was built for — konbini payment, Japanese address validation, and Rakuten sync

Konbini payment integration uses Shopify's Payment App API, which allows external payment providers to be integrated into the Shopify checkout. The integration requires building a payment provider app that: presents the konbini payment option in checkout, calls the GMO Epsilon or Komoju API to create a payment session and issue a payment number, displays the payment number and konbini instructions to the buyer on the payment pending page, listens for a webhook from the payment provider confirming that the buyer completed payment at the konbini, and updates the Shopify order status to paid via the Admin API when payment confirmation is received. The full flow typically takes up to 3 days for the buyer to complete payment, so the order management logic must handle pending konbini orders correctly.

Japanese address format issues are resolved by adding a postal code autocomplete integration to the Shopify checkout. Japan Post provides a postal code API (https://zipcloud.ibsnet.co.jp/api/search?zipcode={7-digit-code}) that returns the prefecture, city, and town for a given postal code. A Shopify checkout UI extension adds a postal code input field that queries this API and auto-populates the prefecture and city fields when a valid postal code is entered. Address field ordering — postal code first, then prefecture, city, town, block number, building — must match the Japanese convention. Without this, Japanese buyers encounter a Western address form that does not match how they understand and write their own address.

Shopify-Rakuten inventory sync requires a custom integration app using Shopify's Admin API (specifically the inventory_levels/update webhook and the Products API) and Rakuten's RMS Web Service API. The integration handles two sync directions: when an order is placed on Rakuten, the app calls Shopify's Inventory Level API to decrease stock for the corresponding SKU; when stock changes in Shopify (due to a Shopify order, manual adjustment, or stock receipt), the app calls the Rakuten RMS API to update the inventory on the Rakuten listing. SKU alignment between the two platforms must be established at setup — Rakuten uses its own item management number (商品管理番号) system, which must be mapped to Shopify variant SKUs.

A Japanese 領収書 generator app is triggered by the Shopify orders/paid webhook. The app receives the order data, formats it according to Japanese receipt conventions — recipient name (宛名), amount in yen with kanji number notation optional, payment date, seller name and registered address, and a revenue stamp notation for amounts above ¥50,000 — and generates a PDF using a PDF generation library (PDFKit, Puppeteer, or equivalent). The PDF is sent to the buyer's email as an attachment. The app should also provide a link in the Shopify order confirmation email for the buyer to download the receipt. The recipient name field requires special handling — Japanese business buyers often want to specify a company name rather than the individual buyer's name, requiring a custom checkout field.

Custom payment integrations for Japan are built using Shopify's Payment App API. This API allows third-party payment providers to appear as payment options in the Shopify checkout flow and handle the payment session lifecycle. For konbini, bank transfer (furikomi), and Japanese credit card processors not available in Shopify Payments, the Payment App API is the correct integration point. The integration requires a Shopify Partner account, a public or custom app with the write_payment_sessions API scope, and a backend server that handles payment session creation, status updates, and webhook processing from the Japanese payment provider.