I think many people are still unsure about which prepaid SIM is the best. The appeal is that you don’t need identity verification or a credit card to use it, but there are so many options—from those available at convenience stores to online-only ones—that it can be overwhelming.

After trying 14 different prepaid SIMs, I realized that the recommended choice varies depending on your用途. If speed is a priority, JAPAN PREPAID SIM is quite excellent. Since it’s a direct SoftBank line, it runs smoothly even during peak congestion times. However, the 50GB plan costs over 6,000 yen, which is expensive for everyday use.

For cost performance, I recommend HIS Mobile. Unlimited data for 30 days at around 3,500 yen is really cheap. It slows down during daytime in the city center, but outside those hours, it’s acceptable. The downside is that you can’t buy it at convenience stores.

If you want to buy immediately at a convenience store, IIJmio JAPAN TRAVEL SIM is the only option. It’s easily available at Lawson and Don Quijote, and with eSIM, it can be activated in 5 to 10 minutes. The price is higher, but in a hurry, it’s understandable. From February 2025, it’s also available at drugstores, increasing where you can purchase it.

For temporary return trips, Nippon SIM for Japan isn’t bad either. 50GB for 30 days at 4,480 yen, no pre-registration needed—just insert and use. It’s also sold at electronics stores, which can sometimes make it easier to get than convenience store prepaid SIMs.

However, the通信速度 can vary quite a bit depending on the time and location. Many services slow down in suburban areas during the daytime, so choosing based on your用途 is important. If you’re using it as a secondary device for long-term use, options like Rakuten Line’s calendar-world or HUAWEI-minwifi are worth considering. Plans with 3GB/month for 12 months keep the monthly cost low.

Ultimately, if you want to buy immediately at a convenience store, your options are limited. But if you have some time, buying online offers more choices in terms of price, speed, and plans. It’s best to organize your usage needs and priorities before making a decision.