Yuki Samejima, the younger sister of Ranmaru Samejima, resides alongside her brother and grandfather in their family’s ancestral kendo dojo after their parents’ passing. Her brother’s deepening connection with Kei Enjouji, shaped by trials they endure together, serves as a recurring thread in Yuki’s daily life, influencing her perspective on loyalty and kinship.

As the story unfolds, Yuki rekindles a romance with Takuma Ban, her high school sweetheart. Their bond strengthens steadily, leading to marriage shortly after graduation and the birth of their son, Takumi—a journey chronicled in a dedicated spin-off that traces her evolution from devoted sister to nurturing mother.

Yuki’s interactions frequently illuminate her brother’s fiercely protective nature, especially during clashes linked to yakuza entanglements and intimate family struggles. Though her narrative role supports broader arcs, her presence remains interwoven with the central themes of resilience, sacrifice, and the unbreakable ties binding the Samejima family.