Ore wo Shiranai Kyou no Kimi

Ono is an honor student who's only curt with Mikuni for some reason. At first, Mikuni was bothered by this, but became engrossed by the casual smiles and gestures from Ono. However, after witnessing Ono being assaulted by their teacher, he can no longer interact with him the way he used to and avoids him. One night, he learns that Ono committed suicide... Mikuni is in despair, but in the next moment, time has returned to the Friday before Ono died...
br> (Source: JP Renta!)

Note: chapter count includes an extra