A one-shot from the first volume of the anthology “Hirari: Extra Issue Girls’ Club Anthology After School!“

Kogane is a socially clueless, glasses-wearing girl who works at a convenience store. She has a huge crush on her manager, Fuuta, but he doesn't seem to return her feelings at all. Luckily, Kogane has a little sister, Akane, who is much more fashion conscious and adept at social situations. Akane is determined to help her awkward big sister get the boy she wants!

Daisuke is a 23 year-old new schoolteacher. He ends up being put in charge of a 3rd grade elementary school class since the previous teacher quit, and in that class there's a girl who's quite a troublemaker--Rin Kokonoe. You could call her a masegaki (used to describe a kid that acts more like an adult in some ways), and she's also part tsundere (though more dere than tsun).

Fujimaki barely scrapes by in school grade-wise. But he thinks all is well, because he just has to quit school and become a top-selling mangaka. It is that easy!
One day he catches his hyper-intelligent classmate Yukimori masturbating to ero-manga in an abandoned room in school. One thing leads to another and he gets blackmailed into drawing ero-manga for her.