Maru

Name: Maru
Nickname: Pedro Martinez
Date when found: Sometime in September
Star Sign: Dog... is there such a sign?
Blood Type: B (just guessing)
Hobbies: Sleeping, eating, playing and taking walks
Skills: Shaking hands (just learned) and jumping
Favorite saying: "Here's your food!" and "Let's go take a walk!"
(Source: "KimiTodo Friend Notebook" extra at the end of vol. 8, Kazehaya answered for Maru)

Maru is a stray dog that Sawako and Kazehaya both saw on their way to school. Kazehaya ends up taking him in and keeping him. He later gets his name, Pedro Martinez, from Pin and his nickname, Maru, from Sawako.