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 rolls the gacha, his oshi (favorite) just won't drop ... Just as his funds are running dry and he decides his next pull will be his last ... Taiki suddenly finds himself 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 instead, it turns out to be a brutal, fiercely female-dominated hellscape! Will Taiki be able to make it out alive ...?! (Source: Kadokawa, translated)