Okay so it was a collection of oneshots from different authors. The chapter I'm looking for was the first one.
So there was a girl with glasses that was called the "walking sex dictionary" (or something like that) by her friends and she helps them with whatever their sexual doubt is.

One of the MC's friend's boyfriend's friend is also called "walking sex dictionary" and wears glasses, too.

One day one of the MC's friend goes somewhere with her boyfriend and the MC receives a call from their friends saying "x and y have gone, we have to find them". The MC goes with male walking sex dictionary, they find x and y, then the two MCs take each other's glasses off and discover they're hotties.

Thx uwu

Karada no Iinari from Love Kare