They're saying that chocolate can give you a nosebleed, but since they don't have chocolate, they won't, so Minoriko punched Shizuha in the face to give her a nosebleed anyways.
Haha...Onee-chan...Gah?!A nosebleed!That's great!It's happened!I'll...Yeah, if you eat too much chocolate,a sweet potato.you'll get a nosebleed.That'sDid you get any chocolate, Onee-chan?That's true... If you don't get any...Then you don't have to worry about that sort of thing...Well, then,Punch
