NTTdocomo, au, and Softbank are all available, but docomo has the widest coverage.
However, please note that there are places where you may not be able to get a signal due to the location of the base station or the terrain.
Also, the connection may be unstable during bad weather conditions.
Wi-Fi is available at an increasing number of accommodations and facilities, but it is not common yet.
Mobile Wi-Fi routers are also available, but we recommend that you check in advance because there are areas with no coverage.