Classmate of Natsumi, known as Mutsumi Hojo in the manga. A poet/artist/philosopher who skips class a lot. He has his own radio show which Natsumi listens to. His partner is Sergeant Major Kururu (Kururu-sōchō), who gave him a pen that allows him to draw anything and make it appear. In the manga, Mutsumi first met the Sergeant Major when the Keronian tried to strike off on his own and turn the students of Saburo's school into his servants. The reason that the two get along so well is because they share the same wavelength. Saburo is a genius, who got a perfect score of 300 out of 300 on an IQ test, and is excellent at sports as well. He has a hard time fitting in with his classmates (especially the male ones) because of this. Although Mutsumi is extremely clever and observant, he seems unaware of Natsumi's crush on him. Every time he comes near Natsumi, he is pushed aside by a jealous Giroro. Mutsumi also makes a few appearances in the anime series Seven of Seven. His nickname comes from a form of Japanese number wordplay.

His name is Saburo in the anime and Hojo in the manga.