Kami Skill (Kokyuu) Suru Dake De Level Up Suru Boku Wa, Kamigami No Dungeon E Idomu summary:

Before you ask, it’s not an isekai.Anyway, the MC is an ordinary peasant who becomes an adventurer after his sister gets cursed by a witch and he needs to find a cure. But the twist this time is that he only knows the skill of [Breathing]. Like, regular breathing.Anyway, how will our hero fare in the endless dungeon, using only breathing techniques to push through, aided by his busty childhood friend who has no romantic interest in him?Look, this is from the same author of that series where a Playboy becomes a Sage and gets two shortstacks to join his party. You know he’s going to find a way to make breathing overpowered, and you know he’s going to have a harem. Why are you even reading this synopsis if you already know it’s going to be one of THOSE stories? Why have you already added it to your follow list when you could read anything and receive a better value? Why are there thousands of delicious and nutritious foods around and you keep eating the dirty quarter pounders right outside the McDonalds dumpster?