Suki Suki Wan Wan!

Kotaro Yukii is a 26-year-old man without dreams or desires in life. When he was a child, he played baseball with fierce determination. Since then, he hasn't given his best to anything else. After quitting his job, he spends his days meaninglessly, living in a house that his parents left behind. His life changes when, one day, a mysterious man appears in front of him. He introduces himself as Kotaro's former pet dog, Ten, and asks to move in with him. Could this man really be Ten?
(Source: AsianWiki)