Yo, Amu.

When you thought the guy you truly had feelings for was picking on you confesses before leaving to search the world to find his father.

That's what happened between Hinamori Amu and her only one; Ikuto.

Amu is now 18, making Ikuto 23.
Amu never got with Tadase. She told him her real feelings and they've been nothing but friends.

With Amu turning 19 soon Ikuto wanted to surprise Amu with his return. He had found his father and kept in contact with Utau, but chose to not talk to Amu for personal reasons.