Souichirou-san

Japanese name:	惣一郎さん
Nickname:	dog

A large, white, "mangy" Samoyed dog, found as a stray by Soichiro Otonashi. He was originally named "Shiro" ("Whitey"), but he only responds to the name "Soichiro" and so Kyoko insists on calling him "Soichiro" in memory of her husband. Other than providing comic relief, he serves to remind both Kyoko and Yusaku of the man he was named after, and serves as a foil to Shun Mitaka. Kentaro enjoys playing with him and considers him his pet. In Ranma ½, volume 7, page 158, Soichiro's name appears on a box saying "Please take me home. My name is Soichiro" while Happosai is hiding under it.

wikipedia