Mr. Yotsuya is a strange man who likes to spy on the other members of Maison Ikkoku. He is fond of crawling around on his stomach and punching holes through the walls at Maison Ikkoku.
He is known as "The alien from outer space". He professes to hold a job, though no one has ever been able to figure out what it is, and he is free to come and go as he pleases. He once told Godai that if he told him, he would have to kill him. He often blackmails Godai out of food and other goods, using his peepholes to spy on Godai's doings.