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.
Huh? Oh, no reason.
¿Eh? Oh, por ninguna razón.
¿Eh? Oh, por ninguna razón.
Hein?
 Ah, nenhum motivo.