Ore wa Nayuki o Wasurenai

Yuichi saves Akiko from the approaching truck, but loses memory himself as a result. Yuichi returns to normal life with only aftermath memories, but life gets gradually distorted because of that. Akiko feels her responsibility and is further depressed by her mother's death. Nayuki feels a gap because old memories aren't shared by Yuichi anymore.

"I want to go back to the days when we all lived happy together..."

[From vndbreview]