Souichirou is Kyoko Otonashi's pet dog.

He serves as the perfect hindrance to Shun Mitaka's pursuit of Kyoko.

He was first found as a stray by Souichirou Otonashi. His original name is "Shiro" ("Whitey"), but he only responds to the name "Souichirou" and so Kyoko insists on calling him "Souichirou" in memory of her husband. He is always in danger of being lost because of following food carried by strangers.