Men at Work! 2 ~Hunter Academy e Youkoso~

A Hunter Academy was established to teach Monster Hunters.
Cliff came to the academy to become a Hunter,
but the place turns out to be an old building unlike its name suggests,
and the great Hunter couple who was supposed to teach him leaves the Academy to go solve an incident in another town.
The Hunter candidates are all girls except for Cliff.
And after many turns of events, Cliff is placed in charge of the Academy and gets to stay with all the girls...

[From mirrormoon]