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Hai Seturn is one of the goddesses ruling over the ancient nation of Seturn. Neptune describes as similar to Nepgear in appearance. It is likely she is also similar in personality to Nepgear
Hai looks like a young teenager. She has long hair with a single snake hairclip. Hai, similar to her sister Vee wears Eygptian themed clothing. She wears a sleeveless top that exposes her midriff. She also wears two long white gloves. Hai has glasses, and a choker necklace with a jewel in the middle. Hai also wears a circlet that her hair generally covers and a loincloth.
Hai Seturn's personality is not well known due to the fact her adventure in Neptune was not in the manga. However, it is likely she is similar to Nepgear in personality being a diligent hard working girl that gets distressed easily.
Main Article: Hai Seturn/Relationships
Anime & Manga
Hai Seturn is a minor recurring character that first appears in Chapter 10. It is implied Neptune ran into her after she got lost in the underground caverns of Dreamcass Island.
The two likely explored the underground caverns looking for their respective sister. Likely Neptune leads Hai but triggers all the traps require Hai to save her. Eventually Neptune likely hears Nepgear and runs off.
Hai also meets her sister as well but disappears from the Planeptune sisters. Later, the two sisters find a beach ball, the same one Neptune dropped to get lost in the underground caverns in the first place.
The Seturn sisters as a whole make a reappearance in Chapter 37. Seeing that Neptune is pinned down by ASIC and Nepgear is being threatened. Vee Seturn and Hai Seturn decide to give Neptune a bit of CPU power so she can transform again. Neptune transforms and Purple Heart defeats ASIC with that.
Vee asks her sister if she thinks they gave them too much help. Hai does not think so. Vee asks if she has taken a liking to them. Hai agrees she has. If that is the case, there is no need to worry about giving them power. Vee thinks as long as the Planeptune sisters have their powers, their country will remain safe.