Aoyagi Koharu
The mother of two, Nozomi and Riku, formerly known by the maiden name Takamura. After her husband, Shin, passed away in an accident, she juggles multiple part-time jobs while raising her children. Following her parents' divorce, she was taken in by her father's family, leading to a 20-year estrangement from her biological mother, Sachi. They reconnect when Sachi applies for public assistance. Awkwardly, she addresses Sachi as "Mrs. Uesugi."
Experiencing dizziness during work, she receives a diagnosis of aplastic anemia from Sawamura. Despite keeping her illness and medication a secret, she resolves to confront and survive the disease. Considering the possibility of the worst, she and her children move in with the Uesugi family. Later, she discloses her illness to Nozomi and Riku.
She believed there was no need to know the details of the accident that caused Shin's death, but when Shiori reveals the truth, she is deeply shaken. However, while pouring out her feelings to Sachi, she finally starts calling her "Mom."
Initially intending to refuse Shiori's bone marrow donation despite the compatibility, she eventually accepts it. Faced with the absence of a suitable donor in the bone marrow bank and the concern that the children growing attached to Shiori might turn that affection into resentment in the future, she undergoes the surgery and successfully recovers.
(Source: Japanese = Wikipedia || Translation = MyDramaList)