Young Nozomi became pregnant and gave birth to Tatsuki. Despite being mother and son, their close ages allowed them to maintain a surprisingly good relationship. On holidays, they often went shopping or traveled together, spending time like close friends. One day, during summer break from university, Tatsuki invited Nozomi on a hot spring trip. Expecting another fun getaway together, Nozomi looked forward to the journey. However, Tatsuki had a different motive—he wanted to discuss something important.