Valt: steals everyone else's candy

Shu: watches spooky videos on YouTube and then shows them Valt so he can't sleep that night

Rantaro: throws out all the candy he gets and just keeps the lollipops

Daigo: wears his regular clothes and calls it his costume

Wakiya: doesn't do anything because he says that 'halloween is for kids'.

Ken: dresses up as Sailor Moon and ends up getting the most candy out of all of them until Valt steals it