The universe is based on Marvel and the DC Animated UniverseGiven how its a crossover of japanese superheroes come together with new adventures its not surprising.
Sailor Moon is the universe's equivalent of SupermanI know, even though Goku is a Superman expy, Sailor Moon is one since some of the O Cs are base on Darkseid and Lex Luthor.
The Demons of Makai/Meikai have relations to Onimusha
Pairing theoryIn a yet-to-be-written installment, Rika Nonaka will get together with not Takato Matsuki, but Zoe Orimoto. Because as near as I can tell, it honestly seems to be what the author's planning, crack-shippy though it is.
Dawn of Chaos pays a big tribute to Dissidia Final FantasyThink about it, an ultimate showdown between the forces of order and discord.