6 decades books

When magical beasts cross into Japan through portals, magical huntresses (and some magical huntsmen) are there to slay them. Consisting of a group of teenagers and young adults working semi-independently under the guise of the Protection and Research Agency, they fight day in and day out for a variety of reasons, using special rings to transform and gain weapons to use in their battles, for which they get paid for each magical beast they kill and bonuses if they save anyone attacked by them.