18+ Saijaku to Yobareta Kentoushi no Game Chishiki Musou: Josondanpi Sekai no Colosseum de Nariagaru

Taiki is a heavy-spending "whale" who lives for his favorite character. No matter how many times he pulls the gacha, his favorite just won't drop... With his funds running dry, he decides his next pull will be his last... and that is when Taiki is reincarnated into the world of "Arcana Campus," the game he had poured his heart and soul into. He thought he'd be able to build a harem of female characters like angels and elves, but it is a brutal, hellish land where women are superior to men! Will Taiki be able to survive...?!

(Source: Kadokawa, translated)