Tensei Colosseum: Saijaku Skill de Saikyou no Onna-tachi wo Kouryaku shite Dorei Harem Tsukurimasu

Synopsis

Average high school student Mikagami​ Kouji is a hardcore gamer. One day he gets isekai'd and he only gets the skill "copy" which is apparently useless but we all know it's secretly OP or something. He's enslaved to be a gladiator by his summoner, the big booba, head priestess Zayd. He has to fight in the Colosseum and if he loses he gets raped.