I’m an Alchemist Who Doesn’t Know How OP I Am

In order to save her little sister's life, S-ranked adventurer Laffey seeks an all-healing elixir. However, elixirs are highly precious items that take years to make by even the most experienced of alchemists. But one day, she meets a man that defies these rules! "Here, an elixir. Oh it's fine, I can always just make more." A slow-paced fantasy about an extraordinary alchemist who doesn't know his own worth and the beautiful adventurer who gets caught up in his efforts to help others! Source: MANGA UP!