Shun's younger brother Fuyuki and his girlfriend Mamiya-san kissed.  When Shun finds out, he asks his friends what he should do as Fuyuki's older brother.
Fuyuki ignores his brother and goes on a date with Mamiya.  The gang decides to follow the couple on their date and end up at a karaoke box.
Mamiya-san's parents aren't home today,
Los padres de Mamiya-san no están en casa hoy, así que pueden estudiar en su habitación sin interrupciones
Los padres de Mamiya-san no están en casa hoy, así que pueden estudiar en su habitación sin interrupciones
Os pais da Mamiya não 
estão em casa hoje,