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.
Why would you make the 
girl you love cry?
Por que você fez uma garota 
que você ama chorar?