JR East just released more details regarding its experimental hydrogen fuel cell trainset, the FV-E991 "HYBARI" will be a joint effort by Toyota (full cell), Hitachi (hybrid propulsion), and JR East (hybrid propulsion and the actual train itself) with the prototype 2-car set to be built and go under testing by March 2022 on Tsurumi / Nanbu Lines
https://www.jreast.co.jp/press/2020/20201006_4_ho.pdf