His chara is Kiseki and his chara-nari(transformation) is Platinum Royal. He grew up with Ikuto and use to call him "oni-tan" (Brother). Also he grew up with Utau Hoshina(Tsukiyomi). Tadase has progressed from the begining of the series from a shy boy, into a more confident pre-teen.
He forgives Ikuto after he finds out he was merely a puppet to Easters scheme. He later tells Amu that if she loves Ikuto, she should go for him. That is when I realized:
"Hey, he's not a little kid anymore, he's a guy who loves a girl a lot." I mean anyone who's willing to give a girl up to the guy they use to hate for a long time is mature.