Nanaumi is a woman that appears to be in her mid 20's. She usually has a grin on her face, showing her blackened teeth. The right side of her hair is white with a small section of black, and colors are opposite to her left. She has a large chest and her clothes mimic the black and white scheme of her hair. She has a katana that all of the Kina servants, plus their king, have. Thus far, she has never been seen without her eye mask on.
Nanaumi is usually not that friendly to others, except for her lords and ladies. She is loyal and kind to them, as shown, when she was in Kina with Takeruhiko and the others, she tried to keep them company and she assisted them whenever they asked. As for other people, she becomes a little childish and forgets her manners, starts doing pranks, laughs when somebody does something stupid, does not agree with an opinion different than hers and gets angry when somebody tells her the truth about something. Despite that, she is a very clever woman. She supports people and gives a honest opinion. She seems to like war as she claimed to be excited at the prospect of the incoming war.
Nothing is known about her past, except that she is serving Takeruhiko from a long time ago.
Nanaumi joined Hakuryuu Ren in the civil war of the Kou Empire. Nanaumi asks Hakuryuu if he wanted to let Aladdin get away and that if he wants to have Aladdin as his ally. As Hakuryuu demands more Magoi from Al-Thamen's dolls, Nanaumi notes Hakuryuu cannot move his artificial arm anymore. She expresses concerns when Hakuryuu overexerts himself and notes Hakuryuu was aware of his own exhaustion. She remarks it is a pity and a lost cause that Hakuryuu cannot win against his siblings. While Hakuryuu struggles, Nanaumi explains in further details that Hakuryuu cannot win against his brothers in direct combat by pointing his inability to move his arm and legs due to the lack of Magoi. She smiles that when her master lends a hand, the result of the civil war has been decided from the start. When a surge of water arrives, she happily greets her lord. 
Nanaumi is loyal to Hakuryuu as she pledges to fight alongside him.
Nanaumi appears to be very fond of Takeruhiko as when he appeared on the battlefield, she started jumping in happiness and said that she has been waiting for him.  She is crazy impressed by his actions and comments everything that he does. She usually sighs and then says something in the sort of `amazing!` and gathers her hands in delight.
She claims that she hates Sinbad and because he is known as the "High King of the Seven Seas" and she thinks that it is like he is ruling her as well. 
She usually scolds Nashime angrily when he says unnecessary things about Takeruhiko. 
- The kanji in her name mean "Seven Seas", possibly alluding to her allegiance to the Seven Seas Alliance or Sinbad.
- Nanaumi's black teeth is a practice of Ohaguro, or dying one's teeth black. This may refer to the ghost story Ohaguro Bettari , which is about a beautiful looking ghost who pranks men.
- In the Magi Volume 37 signing board, Nanaumi wrote her wishes to marry her lord by signing her name with her lord's last name, "Yamamoto." She's not officially or confirmed to be married to the lord.