A wingback for Tohoku Select; his jersey number is 7. He's usually called Mitsu. At one point he lived in Tokyo, where he met Koiwa Teppei, who he beat in a race. Because of him, Teppei took up soccer.
He's much more sportsmanlike when he loses than when he wins.
Mitsu technically first shows up Vol. 16 FEEL THE DESTINY when Teppei is reminded of him by a kid playing soccer who looks like him, and tells Kazamatsuri Shou about how they met and why Teppei plays soccer; his first in person appearance, however, is in Vol. 19 TURNING POINT when he asks his teammate Itai Yudai about his information gathering on the other teams at the National Toresen. (Yudai calls him Mikkun rather than Mitsu. Considering that he calls him "Mitsu" later during the Tokyo v. Tohoku game, this could either be because the translators didn't recognize him and misread "Mitsu-kun" or just the author's way of obscuring Mitsu from recognition until he comes across Teppei later on.)
Mitsu clearly plays off his speed, both in running and in ball control--unlike Teppei, he's good at not letting the ball get away from him. He and Abe Kotaro are the main force behind Tohoku's offense, so they can coordinate better with one another than most of Tohoku, which has shaky teamwork from being unable to pratice during the winter. Ultimately, however, they usually don't need to do much in terms of strategy besides run around and create chaos, because no one can really catch up with them.