Based on

TV Shows like Monster Strike (2015)

Ren Homura returns to his former residence, yet he feels very uncomfortable: he possesses no memory of having lived there. Without warning or his permission, a game called "Monster Strike" installs itself into Ren's smartphone; monsters of the game then literally fly out from his smartphone and start fighting on streets. Watching the fighting in amazement, Ren starts picking up his lost memories.