I'm really confused about which cheap SIM that offers 20GB to choose. I’ve recently looked into various options, and I realized that it all depends on what you prioritize the most.

If you want a balance of speed and cost, au's povo is truly excellent. With a basic fee of 0 yen and a topping system where you only buy the data you need, it's easy to customize according to your usage. The effective cost drops to about 2,163 yen when using 20GB, which is quite cheap among major carrier providers. Since it uses au's network directly, it’s also less likely to experience speed drops during congestion, which is subtly important.

However, if you want to pay the same amount every month for peace of mind, ドコモ’s ahamo and ソフトバンク’s LINEMO are also good options. ahamo offers 30GB for 2,970 yen per month and supports international roaming, while LINEMO includes unlimited LINE usage. The speed reduction during certain times of the day is also barely noticeable with these plans.

On the other hand, if cost is the top priority, 日本通信SIM’s 20GB plan is the cheapest at 1,390 yen per month. As an MVNO, there’s a risk of slower speeds during the daytime, but being able to use a 20GB SIM for just over 1,000 yen is attractive.

For those who want more network options, mineo is also worth considering. Being able to choose from ドコモ, au, or ソフトバンク networks is convenient. However, the initial cost is relatively high.

Ultimately, the choice of cheap SIM depends on whether you prioritize cost, speed, support, or network options. Organizing your usage and priorities before choosing is the key to avoiding mistakes.