The Sun of S

(from ebookjapan):

Suddenly abandoned in a strange town, a puppy named S is picked up by a kind girl named Yumi in a residential area with a view of Tokyo Tower. However, Yumi's father has to return to Kyushu in ten days for business reasons, and S and her pups, Kuma and Marie, are left in the care of different homes.

The three dogs and their cat, Mee-kun, who really wanted to see Yumi, decided to make the long, long trip from Tokyo to Kyushu, where Yumi was staying...

Leiji Matsumoto depicts a sad but beautiful and moving story of people and animals. Includes two stories, "Sun of S" and "Midnight Sun Rina".