Seijo Celestia no Keikenchi

The story is an erotic comedy about Celestia, a priestess who fell in love with a knight. Although her status as a holy priestess required her to remain pure, Celestia wanted to have an intimate relationship with the knight, so she devised various schemes to tempt him into making the first move.

(Source: Natalie.mu, translated)

Note: Originally a three-chapter limited run titled "Midara na Seijo-sama no Keikenchi", the title was changed for the extended serialization.