Kazuyoshi Usui's younger brother. Masafumi is a year younger than his brother. He is brilliant with computers, and possesses a very scientific mind. He created the speech synthesis software that Switch always uses.

Spoiler

He is the original source of the "Switch" nickname. The reason for his nickname was because he was called Usui-chii by his friends and it sounded like "Switch". Thus, it became his nickname.

Spoiler

He was killed by Yukino, who mistakenly believed that he and Sawa were dating.

(Source: SKET Dance Wiki)