I tried several prepaid SIM cards, and to be honest, the recommendations vary quite a bit depending on the service. You need to choose based on your usage needs.

First, if you want to use without worrying about data limits, HIS Mobile's prepaid SIM is a good option. It offers unlimited data for 30 days at around 3,500 yen, which is attractive. Since it uses the Docomo network, there are generally no issues, but speeds can slow down during daytime in the city center. However, at night or in suburban areas, it’s comfortable and perfect for everyday use.

If you prioritize cost performance, Nippon SIM for Japan is also quite good. 50GB for 30 days at around 4,500 yen. It’s easy to set up and can be used immediately after purchase. Speeds are stable after evening, but tend to slow down during the day, so keep that in mind.

For the highest speed, Parrot Bee’s JAPAN PREPAID SIM is the best. Since it’s directly connected to SoftBank’s network, it’s stable regardless of the time of day. 10GB costs 2,380 yen, and 30GB is 4,480 yen, which is cheap for large data volumes. However, 50GB costs over 6,000 yen, making it more expensive.

If you need it immediately at a convenience store, I recommend the IIJmio JAPAN TRAVEL SIM. You can buy it at Lawson or 7-Eleven, and eSIMs can be activated in as little as 10 minutes. However, compared to others, the price is higher—10GB costs 3,280 yen.

When choosing a prepaid SIM, it’s important to balance price, speed, and ease of purchase. If you plan to use it for a long time, focus on cost; if you need it immediately, prioritize ease of purchase.