I have a good relationship with Takagi, boasting to everyone that Takagi and I are "WATARU brothers" (Ye in Gao Mushe and Hang in Date WATARU are pronounced "WATARU" in Japanese). Associate with English teacher Natalie Lai.
After completing a surveillance mission, on the way home, in order to show Takagi a notebook, he was knocked down by a tired driver when he picked up the notebook that fell to the ground. Ida originally planned to take her parents to Hokkaido to meet her girlfriend Natalie and her parents that day, so before she died, she gave Takagi a notebook with Natalie's photo sticker and engagement ring on it, hoping Takagi could fulfill her wish. Since then, Takagi has been recording in that notebook, making constant efforts to become an excellent criminal police officer like Officer Ida.
Natalie hanged herself at home that day because she was heartbroken when she learned of Date Wataru's death. Because Natalie left an email "WATARU will never come back" before her death, the elderly teacher in the oral English classroom with her mistakenly thought that Natalie was abandoned by Gao Mushe (pronounced WATARU) and committed suicide. A year later, on Memorial Day, he kidnapped policeman Takagi in Hokkaido. After the prisoner committed suicide by taking poison, Takagi was successfully rescued by police officer Sato.