Hito no Musuko

Asahi Suzuki, a manga artist, receives a letter from Takamine Yamamoto, a student from his nursery school days. Feeling nostalgic, Suzuki meets Takamine and deepens their relationship. Takamine had left his mother and was living in an orphanage.
Is it possible to raise someone else's son?　
Does it matter if a family is not blood-related?　
A story of a single man in his thirties and a boy.

(Source: Kodansha, translated)