You remembered what Mahito had done to him. It was vivid in your mind. The pain and emptiness was unbearable to you. Without Nanami, life lost its meaning.

So you went back in past a few times to save him. Unfortunately, it ended in the same fate. But if there was one chance out there. It would be your only chance to save him

You are back in the past. Back from where it all begun. This is just another chance to save him and you won't let it go.