Hana Somei/Plot

Background
Somei grew up in Mikado City, next door to Yōko Katori's family. The two are childhood friends, with Somei often visiting Katori during her breaks from study. Somei was forced by her father to study continuously in order to maintain high marks, though Somei did it principally for the benefit of self-awareness. For her part, Katori put hardly any effort in her studies, but got better grades than her friend. When Somei failed to rank first in her cram school's tests, her father forbade her from going over to Katori's. She thus swapped rooms with her brother and had a window installed so that she could talk to her friend without either leaving their room.

Four and a half years before Yūma Kuga and Chika Amatori joined Border, Katori and Somei lost their homes in the first large-scale invasion. Somei dug Katori out of the rubble, which was trapped under the rubble, rescuing her over her own family because the roof of her house looked lighter. At the hospital Katori found her family safe and sound, while Somei's passed away. Somei lived at her cousin Yūta Miura's for a while. Two years after the attack Somei decided to enlist in Border and aim for the top, which prompted Katori to follow her. For the past two seasons of rank battles Katori Unit managed to stay in the top group of B-rank.

Introduction Arc
Katori Unit was presumably involved in the extermination of all Rads in Mikado City.

B-Rank Rank Battles Arc
After Tamakoma Second's victory in the match against Suzunari First and Nasu Unit on Februray 8, Katori Unit drops to the middle tier of B-rank for the first time in two seasons, later dropping to 9th place when they lose to Nasu Unit.

Katori Unit is on defense duty on Wednesday February 19 and they make short work of a group of Mole Mods. Katori complains about having defense duty on the day before a match, sparking an argument with Rokurō Wakamura. Somei sternly reminds them that they are on official duty.

Minutes before the match, Katori and Wakamura have their most heated fight yet. Somei does not intervene if not to let them know that they match is due to begin soon. When Katori recklessly charges at Yūma right off the bat, Somei directs Miura and Wakamura to support her, warning them when Osamu Mikumo joins the fray and keeping silent when Katori and Wakamura start bickering. As soon as her teammates leave Tamakoma Second's wire zone Somei alerts them to Kakizaki Unit approaching. When the latter team manages to gain the upper hand, Somei instructs her teammates to move to an open space, forcing Tamakoma Second to chase their opponents away lest Katori Unit be wiped out and the points taken all by Kakizaki Unit. Katori Unit and Kakizaki Unit then decide to duke it out among themselves if Tamakoma Second will not leave their wire zone, but Chika proceeds to demolish large sections of the map. Unaware that she is unwilling to injure others, Somei tells her teammates that Kakizaki Unit likely intends to cooperate with them: if they both venture into the wire zone from a different direction, Osamu and Yūma will have to split up to intercept them. Somei estimates that Kuniharu Kakizaki wants them to venture into the wire zone first, as that will increase the chances of their being intercepted by the enemy ace. Somei then proceeds to alert them when Chika activates Lead Bullet and when Kotarō Tomoe bails out.

When Kakizaki also bails out and Fumika Teruya begins moving towards Chika, Somei proposes that Katori distract Osamu while Wakamura and Miura pincer him using Bagworm and Chameleon respectively. Osamu's red wires and Yūma's arrival however result in the plan failing and Miura and Wakamura both bailing out. Somei apologizes to Katori and later warns her about Teruya defeating Chika and then bailing out on her own. After the end of the match, Katori has a meltdown, claiming to want to quit Border, but Somei remarks that she would hate herself even more if she did so, but that she should do so if that is what she wants to do, shocking her teammates with her apparent indifference. Miura suggests that Katori is envious of Tamakoma Second's ability to work hard and proposes that they do the same. Katori doubts that she can do it, but Somei observes that if she feels bad about losing, she has can still improve.