Does anyone know what manga this is?

I read it like 3 years ago, so its pretty old and i dont remember if i finished reading it
There was a really strict woman who was rlly pretty and separated her work and personal life but this guy came along and wanted to become sex partners. She got into a relationship with that co worker and they became sex partners and it was like a game(?) And whoever loses is the one who ends up falling in love. Basically she ends up falling in love and they stop being partners with benefits. I dont remember what came after T^T if anyone knows what this manga is called pls lmk