Hanabusa Seki (関 英Seki Hanabusa) is Tobari's 40-year-old live-in lover. She is a paleontologist and is often away on work-related business. She knows that Tobari is a ninja, but she does not understand any of the details about the ninja world because they've sworn never to talk about any Nabari business under their roof. She is voiced by Kotono Mitsuishi in Japanese and Leah Clark in English.
Hana has wavy dark brown hair that reaches her mid back. She often keeps part of it pulled back with a clip that has a white rose on it. She has light brown eyes. She is 5'4" which is relatively short for her age. Her normal attire is a blouse with pants, she is shown to wear the color pink frequently.
Hana has saved Yoite's life in the past and acts like a surrogate mother to both Yoite and Miharu. She is one to take action and will meddle into other people's affairs when they are too shy or afraid to take any action of their own, gladly offering her assistance to any person in need. This is shown when she knits a scarf for Yoite, just because she was worried he was cold. She often says what comes to her mind without any prior explanation. It is also revealed that she "gets anxious," however Tobari seems to help calm her down and cheer her up. When Tobari doesn't show up at her house after coming back to Banten, she appears to be very concerned and on edge.
- Hanabusa is in a common-law marriage with Tobari. She can be seen wearing a ring on a necklace around her neck, which is a part of a matching pair with Tobari's, which he wears on his ring finger.