Tooru Hagiwara, a shy and caring math teacher at Jougaouka High School affectionately nicknamed "teddy bear," hails from Tokyo. He has a younger sister, Izumi, and a younger brother, Kyouhei. His childhood included a pet dog, Umenosuke, pivotal in his first meeting with the Shibata brothers.

During high school, Tooru encountered Masami Shibata, initially mistaking him for a girl. Discovering Masami's gender didn't alter Tooru's feelings, sparking a lasting relationship that began with tutoring sessions when Tooru faced academic struggles. Early hurdles included Masami's reluctance toward physical intimacy due to past trauma and complications like a misunderstanding involving Tooru's ex-girlfriend, Eiko.

Tooru's dynamic with Masayoshi Shibata, Masami's brother, shifted dramatically. Initially resentful and protective, fearing Tooru would distance Masami, Masayoshi eventually accepted their bond, becoming a supporter of their union. Tooru and Masami married, securing reluctant approval from Masami's father, Yoshiyuki, after initial resistance.

Their interactions frequently involve overreactions and misunderstandings, leading to humorous conflicts. A recurring element is their repeatedly interrupted attempts at a first kiss. Professionally, Tooru interacts collegially with Masayoshi in the teachers' lounge. His traditional parents gradually accepted his relationship with Masami, influenced by his brother Kyouhei's support.

Key developments include Tooru's relationship with Masami evolving from chaste romance to a fully consummated partnership, symbolizing the resolution of earlier emotional barriers. His journey reflects themes of patience and commitment, navigating familial and societal expectations while maintaining his gentle demeanor.