The short answer
With low email open rates in Japan, a LINE Official Account is the most reliable retention and CRM channel. Design friend-adds, segmented messages, and step delivery to automate the post-purchase relationship.
Start by designing the friend-add path: gather friends via QR on ads, stores, and packaging, then prompt a first action with a welcome message and offer right after adding.
Segmented messaging beats broadcasts. Branching by purchase history and interests lowers block rates and lifts conversion.
Design send frequency around message pricing and policy. Step delivery sends automated messages on a schedule after the add to encourage repeat purchase.