Tou no Kemono(2003)

Orphaned, blind in one eye and hungry, Lukka tries to trade his shoes for a meal. Unfortunately, the villagers don't much care for their local homeless cripple and he's shoved into the path of an oncoming carriage. Luckily for Lukka, what could have been a terrible death turns out to be a kind twist of fate. The passenger, Edgar, is a nobleman with striking blue eyes who invites Lukka to help him end his solitude. The two grow as close as brothers and Lukka blossoms into a bright, helpful servant and a loyal friend. But once every month, Edgar leaves the estate for three days and entrusts Lukka to feeding his "pet" in the tower: a beautiful black wolf with clear blue eyes...

(Source: Manga Reborn)