Online only / online-dedicated

オンライン専用 online sen'yō

A plan where application, account management and support happen mainly or entirely online.

"Online only" describes how a plan is run, not just how you buy it. Depending on the plan, several different things may be online-only:

• Application — you sign up on a website or app, not at a counter.
• Support — questions are answered by chat or web form, not by a shop or a phone line.
• Troubleshooting — when something breaks, you work through it yourself with online guides or chat.
• Plan changes — you change options yourself in the app.
• SIM activation — you switch the line over yourself, following on-screen steps.
• A shop may still 'help' with an online-only plan, but that help is often a paid service where staff guide you while you operate your own account.