A character named Regina wants to save the world. In order to achieve that she needs Mason's help and gave him a ring that makes all the ladies around him attracted to him. He needs to have sex with different ladies to make his ring strong so when he faces Lady Merusa she can't influence him to join her.
KTE is just a name for sex so Luna doesn't panic about having sex without being in a relationship.
There are so many things that will make sense when Magic Ring is released.