Haibane when he was infant he thrown away by his parents, Nemu used up her light to save the infant Haibane. She lost her light (hence the name 'teiden shoujo') and raised Haibane, making her Haibane's self-proclaimed mother. When he grew up he became sort of like Nemu's guardian. Since Nemu lost her light, Haibane couldn't see anything. Even so, he was a skilled fighter.
Haibane treasures Nemu a lot and he seeks to find a way to gain back Nemu's light.