That's all there is to the story? A 13/14 year old girl showing her underwear all the time, having the body of a 16 year old (to be generous)? There's nothing more, in 12 chapter nothing happened, there wasn't any developpement...
There were some hint of drama with the girl but there's nothing more than weird fanservice...
That's not even talking about how much of a trash the MC is. The dude dont even have the spin to help a girl by letting her share a fucking umbrella... As if it was a challenge of some kind.