Senju Kawaragi/Synopsis

History
Senju is the youngest among the Akashi children collectively known as the "Mysterious 3 Siblings.” Her eldest brother Takeomi Akashi was a founding member and Vice President of the First Generation Black Dragon before joining Brahman, while her second eldest brother Sanzu was the former Vice-Captain of the Fifth Division in the Tokyo Manji Gang. Currently, Sanzu is a trusted member of the Kanto Manji Gang under the leadership of Manjiro Sano.

While not much information is given about her family, Senju prides herself on having a close relationship with Takeomi. On the other hand, Sanzu finds no interest in her and Brahman despite Takeomi’s endorsements. During a day-off shopping spree with Takemichi Hanagaki, she mentions how Sanzu's detachment from his siblings is what led him to join Kanto Manji.

She uses a fictitious surname “Kawaragi” instead of her factual surname to stay professional in the workplace. However, her true reasons for doing so, as well as her family history, remain unknown.

Three Deities Arc
As Takemichi Hanagaki travels back to the year 2008, Senju appears along with other notable members of the delinquent gangs Brahman, Rokuhara Tandai, and the Kanto Manji Gang who all concurrently control Tokyo as a result of Tokyo's two-year Sengoku Period. She is soon addressed by Kazushi Yamagishi as a charismatic leader of the infamous Brahman, a formidable gang that excels in working in the shadows, and recognized as the current ruler of Shinjuku. On a rainy evening in Tokyo, Brahman clashes with Rokuhara Tandai to recruit Takemichi into their gangs. Senju watches the confrontation from the sidelines, avoiding the spotlight as her older brother Takeomi Akashi leads Brahman in her stead, but eventually performs a surprise attack on Rokuhara Tandai's Representative South Terano in hopes of taking him down. She forcefully thumps his head and faces him, but Shion Madarame comes to threaten her.

To her luck, Keizo Arashi protects her by knocking Shion out. He reminds her that their current goal is to recruit Takemichi rather than to brawl, but Senju tells him off before he gets attacked by Kakucho Hitto. She watches the fight between the gang leaders unfold, until South recovers from her attack and proposes to settle the dispute between them through a one-on-one fight. Senju rejects his offer, adamant in only recruiting Takemichi. Cops arrive as their confrontation causes traffic. Senju leaves with Brahman after acknowledging Takemichi's willpower, then meets him again at D&D Motors where Ken Ryuguji warns Takeomi to not drag Tokyo Manji Gang members into Brahman's plans. Senju explains that the gang's goals align with Draken's to dissolve the Kanto Manji Gang and rescue Manjiro Sano from his dark impulses, and asks Takemichi to join them herself. Draken refuses, but Takemichi accepts.

Once he is welcomed into Brahman, Senju hands him her umbrella and makes him her gofer. She tells him to meet her the next day at three in the afternoon in Harajuku. As they meet, Takemichi is surprised to find out that she is apparently a girl.

In Harajuku, she drags him around from store to store to shop for clothes. Takemichi makes small talk and asks her about Brahman and her relationship with Takeomi who she admits to be her older brother. Senju then tells him that the surname "Kawaragi" is merely fictitious, a name she uses for the sake of professionalism, and mentions the name of Haruchiyo Sanzu, Toman's former Fifth Division Vice-Captain and her second older brother.