One day, the eldest son Kohei woke up in the morning to find that he had wet the bed. Mistaking ejaculation for an illness, Kohei tried to hide it by passing it off as bedwetting. However, when his mother told him that bedwetting was embarrassing, he cried from frustration… Soon after, his sister Tsuna, who had learned the truth from their younger brother, decided to provide sex education through practice since she couldn't explain it well with words…
