Isekai Gaeri No Moto Yuusha Desuga, Death Game Ni Makikomare Mashita summary:

He was living a peaceful life as any normal high schooler would, until one day he and his classmates were suddenly brought to uninhabited island."I'll have you kill each other until there's only one of you remaining."Hearing these words from the man strangely dressed in a military uniform, his classmates panicked. Yes, he was setting up the stage for a death game. One where the strong devoured the weak. The weak would die without mercy and only the strong would taste victory. That was the plan.However, they were unaware that the hero who was hailed as the strongest had just recently returned from another world. The organizers behind the game were already out of luck by the time the game started as the expectations they had for death game that they had worked so desperately to set up would be unwittingly crushed before them.