Am I Actually the Strongest?

Average high school student Mikagami​ Kouji is a hardcore gamer. One day he casually gets isekai'd but he only gets the "copy" skill 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-boobed head priestess Zayd. He has to fight in the Colosseum and if he loses he gets sexually abused.