Multiversal Missions

Kazuki, a Japanese high school student, on his way home from a training session of his school's boxing club, is kidnapped by a hooded guy and taken to a strange, otherworldly room where he encounters a strange, all-powerful entity that gives him a special ability and forces him to go to different universes together with Enea, the guy who brought him to the room, where they have to perform various missions for his entertainment.