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.
This has got nothing to do with you.
Esto no tiene nada que ver contigo.
Esto no tiene nada que ver contigo.
Não tem nada a ver com você.