Here's what I remember (sorry if it's not helping much) :
It's about a NEET who is forced to go to high school by his father to gather some information about some high school girl (I think the girl is probably his father's illegitimate child)
- The male MC really likes lollipops, has black typical hair (not long)
- It's said in the manga that it's easy for MC to win over a person's heart
- His father is a doctor (?), wears glasses, has long white hair (ponytail)
- His mother is an owner of a men's club, wears a kimono and has some connection with the police
The the first girl has a part time job at a cafe.
I remember of some scenes where:
- The MC wraps himself in a blanket, and then his father came.
- The girl gives the MC some bento, the MC gives the bento back along with a lollipop.
- MC helps the first girl cleaning the dish in the cafe.
- MC talks with some fat guy in a hat (which is stalking the first girl) in a cave
- At the end, there's a scene where the manager of the cafe is arrested by police (along with the fat guy) with the help of the MC's mother (wearing a kimono)