the last boss is mostly about -kaja and -kunda. you should use matarukaja (teddie/kanji) and rakunda. he'll boost himself, so you also need dekaja (yosuke). you will NEED dekunda to survive at least once or twice, unless you get really lucky. you probably have dekunda items.
boss is immune to zio, so kanji isn't as useful. its attacks can deal lots of damage, so i wouldn't bring people with low hp either. i did use yukiko, but she had an armor that gave her 100 hp.