I'm a sex knight

That she could not prevent the monsters from damaging the villages, of the Kingdom she serves, made Holy Knight Elayne feel terribly powerless.

One day, a strange old man told her of the Great Oath Tree in the eastern forest. Sealed within this tree was the answer to her wishes, if she freed it. Her mind preoccupied, Elayne went to the Tree in good faith and began to pray.

When she did, before her appeared the demon Succua.

To protect the Kingdom's people. Elayne makes a pact with Succua. Until Succua completes her pact, she is enslaved to Elayne. Was this an act of self sacrifice, or perhaps... satisfaction?

This, is the story, of Elayne's descent from piousness to nymphomania.