Only I can "level up"!? Become stronger by "union" with a beautiful girl! Best partner fantasy! Everyone is gifted with a talent at the age of 15 - "Skill". Chamber was a member of "Dawn", a party that was prominent in the city, although it was made up of only young members. After acquiring a mysterious skill with an unclear "level up" effect, he is expelled from "Dawn"...! Although he was abandoned by other members who gained powerful skills, Chamber continues to work as a solo adventurer. In the midst of all this, he learns the true value of the skill "Level Up". The more enemies you defeat, the more you level up and become stronger... Chamber realized that his own skill was not a "useless skill", he also has a fateful encounter with a certain girl, and ends up spending his days pursuing strength...!