I always found it curious how Tanaka doesn't refer to the hamster as Riko but as Hamu-chan
Probably has something to do with the manga's theme about the importance of bodies in life... maybe it doesn't make sense for him to call the hamster Riko because doesn't have her body or memories or experiences, which made her uniquely Riko
Her and Hamu-chan have the same soul, but are two entities of their own














