Ama Nee -Osananajimi Onee-chan to no Echi Echi Amayakasare Dousei Seikatsu-

The childhood friend who was like an older sister is back as a student teacher!?

Utsumi Shuuhei, the protagonist, had a childhood friend, Anekouji Amano, whom he affectionately called "Ama-nee." However, after her family moved far away due to her parents' job transfer, they drifted apart and lost contact.

Years later, Shuuhei, now the same age as the "Ama-nee" he once admired, attends the same school she did. Yet, he's never been able to forget her.

Then, out of the blue, a teaching intern arrives at Shuuhei's school. To his surprise, it's none other than Amano - the "Ama-nee" he's longed to see again. What's more, during her internship, she ends up staying at Shuuhei's apartment, where he lives alone...

As if to make up for the time they were apart, a sweet and slightly naughty cohabitation begins between them...

Translated from the official website