The most advanced form of internet that is widely available in Japan is so called “optical fiber” or hikari / 光. The most easy provider to deal with that offers a minimum connection is FLET'S. The highest speed option is FLET's 光 Cross.

Most internet service providers simply provide an Internet connection on FLET's. For example, Sakura Mobile, AsahiNet, etc.

FLET's Hikari Cross requires 光配線方式, not VDSL/LAN. equipment.