Tsuyoshi Ohki
Tsuyoshi and Akito are best friends, although their relationship is a bit odd. Tsuyoshi is normally very meek and mild tempered, but once he gets mad, he goes on a rampage causing mass destruction whenever he happens to be. In fact, the only way to stop Tsuyoshi during these rampages is for Akito to give him a karate chop on top of the head.
Akito, and Tsuyoshi are at odds with each other for a bit when they both take an interest in Sana the same time. Once this is resolved, Tsuyoshi and Akito remain friends, but with Sana also involved quite a bit also. Tsuyoshi's last name changed in episode 14 to Sasaki when his parents went through a divorce.