Revival Game of Wandering ReincarnationsSamayoeru Tensei-sha-tachi no Reliable Game; さまよえる転生者たちのリライブルゲーム

Our main character, Asai Manatsu, is the nice guy, who gets isekaid after he got dumped while proposing. Then he dies while trying to save a mysterious girl, but then wakes up in her body?! Bullshit aside, this is just Dark Souls with waifus.