Bubu to Michel: Ameagari no Tenshi

In the land where Michel lives alone after losing his parents to illness, it starts raining Saturday night. On Sunday morning, the rain turns into fallen angels. Michel finds an egg where fallen angel corpses lay scattered, and Bubu was born. This is a story of love and bonding between a boy with a deep emotional wound and an innocent fallen angel.

(Source: Two Virgins, translated)