Tsubaki Mapputatsu is a miko swordswoman whose blade can cut through any substance except nata de coco, a jelly made from coconut milk. Initially employed by a yakuza boss bent on revenge for a past defeat, she was tasked with confronting Mamoru Kagemori. Upon learning the yakuza boss had misled her about the situation, she turned her vengeance upon him and ended her service.

She then chose to enroll in Mamoru Kagemori's school to broaden her worldly understanding and modern knowledge, as her background left her inexperienced in contemporary social customs. She developed an affection for Mamoru after he offered her encouragement and support during a time of frustration over her old-fashioned ways.

Tsubaki now expresses a wish to live as a regular high school student, leaving behind her former life as a hired swordswoman.