Ore to Seijo ga Dekiteru Koto ga Baretara Kono Party wa Houkai suru

Rin, the gloomy-type mage, somehow ends up in a secret relationship with the party's sweetheart, Sophia. But for certain reasons, no one must ever find out. Caught between "We can't get caught!" and "But I still wanna do it!" Rin's heart is ready to explode!