with juntoge - probably something classic horror or easy to wear. because junpei loves horror movies i think she'd get a bit excited, then ambitious, then overwhelmed and burnt out by her own ambition, and also realizing this is going to mean people perceiving her... things like that that don't phase inumaki because he would go along with whatever she said or whatever he thought was funny. so they might do an homage to more classic horror (sadako vs kayako, frankenstein, the invisible man, cabinet of dr caligari) ...something where they can dress up but junpei doesn't have to wear anything that would make her feel too self conscious or too visible.

choita:...i think yuji would find it fun to dress up with his friends. and says choso doesn't have to dress up, until 1. he realizes choso might creep people out if there's just this intense staring man following him and his friends and 2. choso says he'll agree to anything yuji wants. i don't know if they would be matching but i think yuji would try to choose something for choso that covers his intense stare LMAO...and then gives up when he realizes choso seems just as intense when he's in a faceless costume clenching his fists and standing there.

might as well do my other jjk ships now LOL

yutarika: i think it would be cute for rika to be 'visible' on halloween so people just think she's an elaborate puppet...i actually don't know if yuta would dress up. he might if inumaki or yuji coaxed him into it, but i think he'd have fun just seeing rika get attention.

hiita: in a modern au i think they'd be the couple where even when staying at home yuji would dress up...but in canon.....i think higuruma would feel weird. i think he's already very conscious that he's old enough to be yuji's dad and he would die inside if he was out with yuji and someone did mistake him for yuji's father. or he'd tell yuji "i'm dressed as a murderer...[wearing normal outfit] see?" some sort of dry self deprecating answer. he would fold immediately if yuji wanted him to but i don't think yuji would want to make him uncomfortable either, so their middle ground in canon may be a costume they only wear at homebase in each other's company. i do think higuruma would make a cute grim reaper so maybe yuji would be his angel lol.