I knew I recognized some characters! Didn't think there would be manga oneshot spin-off, let alone translated.
I'm pretty sure this is based on the "Hunters" series ( http://hunters.nomaki.jp/ ) and "Kayo-chan" series ( http://www7.plala.or.jp/mashiroyou/kayo_chanSeriesTop.htm ) by Mashiro Yuu:
Premise is that Kayo, who appears in the form of a grade-school girl, goes around introducing herself as a "problem solver". To those that accept, she solves the problem with a twist, transforming people into females. The Hunters organization is formed to combat Kayo, recruit those with the ability to resist or cancel her power, and revert the damages she has done.