Vigilante the Kingcraft Paradise

It is the Early Showa Period in the Imperial Capital of Tokyo. Times are hard but there is talk that times were much worse until a certain "evil" was vanquished. Now Tokyo is in the grips of lesser evils and mysterious rumors...
Especially those pertaining to the "Byakko" and the "Monster of the Juunikai"
Just what are they? Are they something to be feared? To be admired? Or more? And when the "evil" returns... Just whose side will they be on?