Nobody's Boy Remi(1977)

Ie Naki Ko

Remi is a boy living happily with his mother in the French countryside. But everything changes when his estranged father comes home and, in desperate need of money, reveals that Remi is adopted, and sells him. Heartbroken, Remi ends up with Vitalis, a traveling musician, and his troupe of animal entertainers. Together, they travel the country trying to make a living, along the way learning the harsh lessons of life. A deeply moving story about friendship, loss and the pursuit of happiness.

(Source: AniDB)