Sayonara: Dreams of Letting Go

After the tragic suicide of Sayori and a subsequent traffic accident, our protagonist is transported several years into the past where he appears to relive his childhood alongside his best friend Sayori. With vague memories of what's to come, our protagonist must find a way to manipulate the past to overcome the inevitability of his best friend's death. All the while a certain someone observes from beyond.

[From DokiMods]