Yuri Takanashi is the older sister of Yuuta Segawa. After their parents died during Yuuta's childhood, she defied relatives attempting to place them in separate foster homes and raised him herself. To provide stability, she sacrificed her education by dropping out of high school.

Yuri later married Shingo Takanashi, a middle-aged man with two daughters from prior marriages—Sora and Miu—becoming their stepmother. She and Shingo had a biological daughter, Hina, making Hina Yuuta's sole blood-related niece among the sisters. The marriage caused tension with Yuuta, who disapproved of Shingo and moved out.

Yuri maintained an interest in cosplay, shown in flashbacks to her past. She nurtured a close bond among all three Takanashi sisters despite their differing biological mothers, unifying them as a family. This unity later proved crucial.

Tragedy occurred when Yuri and Shingo vanished during a flight; their plane crashed, and they were presumed dead. Relatives then disputed custody of the sisters, planning to separate them. Remembering Yuri's sacrifices to keep him united, Yuuta challenged the family to become the sisters' guardian and prevent their separation.

Yuri's legacy endured through Yuuta, whom their paternal aunt Yoshiko Sahara noted mirrored Yuri's determination and protective instincts while raising the girls. Her absence formed the narrative's core circumstance.

Her relationships define her: sister to Yuuta Segawa, wife to Shingo Takanashi, biological mother to Hina Takanashi, and stepmother to Sora and Miu Takanashi. Her self-sacrificing guardianship established the familial values guiding Yuuta's actions.