魔法使いのタマゴ

Main character is taken by a 300-year-old magician to the forest. There he has to help apprentice girl Miu to become a witch and also comply with the host orders. The way to produce familiars is to place eggs in Miu's body, and he has to help with that as well. He helps to raise a fine demon and hopes to find a way to return home one day.

[From vndbreview]