this manga has a good power system (developed and justified), it has good characters
with good presentation, but the others
they are so poor in development and have crap or useless powers (some).
the main character yuuki wakura has a good justification and explains why he is evolving with the contracts
so i think its a good manga and nice but it has (a lot of fanservice)
many people say "this is not fan service because it is a cost to use power" but brother before fighting literally he does what he wants with her (always sexual)
but I recommend it 100000 times
