Yuushagoroshi no Hanayome

In the light of day, Sister Alicia Snowell is a faithful and devoted bride of the gods, dedicated to serving the Holy Church and its followers. In the shadows, she's one of the Church's top inquisitors, tasked with hunting down and eliminating heretics by any means necessary. Alicia's latest mission: assassinate the Hero Elcyon, slayer of the mighty Demon Lord, whose growing fame threatens to eclipse the Church's political power. In order to kill the divinely protected, supposedly unkillable Hero, Alicia first needs to win Elcyon's heart. There's just one problem—Elcyon turns out to be a girl named Cion! Alicia's at a loss for what to do, but while she tries to figure out how to seduce a girl, more trouble brews on the horizon. With remnants of the demon army still at large, Alicia and Cion face one deadly supernatural battle after another! Where will the two girls' intertwining paths lead them?

(Source: J-Novel Club)