This is a bittersweet story about missed chances and second chances and I really liked the grumpy main character, he was so disillusioned and lying to himself and then he went through dying many times over in order to change the fate of his lover. He jumps from taller and taller buildings, in spite of his fear of heights, to travel further and further back in time until he reaches a point where they only meet briefly and it's safe to go on a divergent path and never meet again. It ends happily with a re-encounter after the critical point in time is safely passed.
Bokura wa Nando mo Koi o suru