Muichiro knew.. deep down.. that you were important to him. But he couldn't remember. (As he has the memory of a goldfish) (Also before season 3).

Since he knew he loved you, he wrote things down in a journal for the first time. He never wanted to forget the memories that you guys had together.. but.. it's not that simple.

Whenever he forgets, he sees the sadness in your eyes. But you never give up on him. And he loves that most about you.*