Reincarnation Colosseum

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.

Alternative : Tensei Colosseum ~ Saijaku Skill de Saikyo no Onna-tachi o Koryaku Shite Dorei Harem Tsukurimasu ~ ; 転生コロシアム～最弱スキルで最強の女たちを攻略して奴隷ハーレム作ります～; Reincarnation Colosseum – Using The Weakest Skills In Order To Defeat The Strongest Women And Create A Slave Harem