Take two if it's Naru or she's there to witness it.
Drink half if she either calls him a pervert or punches him.
Mutsumi says "Oh my!"
Keitaro tries (and fails) to confess his feelings for Naru in the manga.
Shinobu cries.
Every time Keitaro and Naru come close to kissing or admitting their feelings for one another, someone will inevitably barge in on them or Keitaro will suffer an Accidental Pervert moment and provoke Naru into Megaton Punch him.
