Is It Wrong to Try to Pick Up Girls in a Dungeon?, Vol. 1 (manga) — Fujino Omori

Bell Cranel is just trying to find his way in the world. Of course, in his case, the 'world' is an enormous dungeon filled with monsters, below a city run by gods and goddesses who have way too much time on their hands. He's got big dreams but not much more when a roll on the random encounter table brings him face-to-face with the girl of his dreams--but what does a beginning adventurer have to offer a brilliant swordswoman? And what if the lonely goddess who sponsors his solo adventuring gets jealous...?!