Nagi Sanzenin

Nagi is the only heir to the Sanzenin fortune. She isn't just your average "rich girl". Calling her "rich" would be selling her short. The "Sanzenin fortune" is so large, throwing away 20 trillion yen in a red herring investment is considered a prank. Nagi is a short-tempered, spoiled, anti-social or socially withdrawn, hates to lose and to admit her faults, has a considerably hard time confessing her true feelings towards Hayate or anything in the fact of the matter, she acts immature a large portion of the time but is ultimately a good, educated girl. She is good at finance and likes to learn. Her mind is possessed with her own. She cares for her family and friends, but she doesn't want to show her concern directly. She usually tends to show her concern with "formal words". She is a tomboy and tsundere hikkikomori princess. Since going outside is very dangerous because of her status, Nagi favors staying at home. Not liking company in general, she lives away from her grandfather in a "small" (compared to the main Sanzenin estate) mansion with minimal staff. Despite her Otaku NEET-like lifestyle, she is intelligent enough to skip 3 grades at school, which even turns out to be one of Tokyo's most prestigious academies. She has an otaku-level hobby with manga, anime and video games, and draws her own manga. Her Otaku-level is high enough that she has submitted entries for multiple amateur manga competitions, though her entries never won.

Her only surviving family is her grandfather, whom she doesn't like, so she regards Maria as a mother or older sister figure, and warns Hayate not to touch Maria in any indecent way or she will never forgive him. She has a crush on Hayate, and has misunderstood Hayate thinking that he loves her.