It's from the older sister's POV from the start. The younger brother is about to have sex with her and she wakes up. The next scene shows that she's a teacher at her younger brother's school, and she used to defend him, and he fell in love with her. The first chapter is that he keeps on asking her to sleep with him and she gives in. The second chapter is that the older sister's friend (also a teacher at the school), says that her younger brother is only horny and he'll sleep with anyone, and the younger brother proves it's not true when the friend tries to seduce him. The last chapter is the younger brother gets in trouble for fighting with people who've taken photos of his older sister. They end up having sex in the principal's office (I think) and the friend is "guarding" the door and saying how the siblings are so careless.

I read it on doujintoshokan, but can't find it anywhere else anymore.

Many thanks!

I don't know if this will help other people the male guy name is miyuki and the female name is makoto something like i readed that manga too but forgot the name if i remember the name ill let u know

Anekata?

That's it. Thanks for helping