Gosh, holiday ideas!
Open banquet, a parade, a light park lighting (trees, music, food, stalls, exhibitions), a ball at a big 'ol venue in Kyoto or Tokyo, either fancy dress (or dressed fanciliy) or a like, wear winter gear/hideous sweaters thing? Something with volumetric scan photo booths? A pavilion next to professional winter sports going on?
Somewhere with a skating rink, centered around that? There could also be a nod to Japanese Christmas, with fried chicken and white cake.
SASI reminding you to get your end of year fried chicken, from the taisa. It's neko lick'n good!