In the second episode, Kanon and Marin are attacked by their first Monster of the Week, a woman with tentacles for hair. When they combine their attacks and go to finish her off, Marin suddenly stops and says she's seen the monster's eyes before. Then she runs up and hugs her, and it's revealed that the monster was a transformed octopus, and that her hug has changed it back to normal. Rather than kill the Monster of the Week, she saved it.
In episode 7, Marin is unable to use her powers and can't defeat one of Sedna's monsters, so Kanon steps up and successfully purifies it, returning it to the friendly dog it was and sending it back to its owner.
Marin and Kanon saving Urin from Sedna together, even after their powers have been taken away.
Instead of defeating Sedna with a spear of light and killing Urin in the process, Marin and Kanon reach out to her. They hug her, and the power of Marin's love and Kanon's acceptance of darkness moves Sedna's heart and causes her to disappear peacefully.
The aesop of the series. Everyone has darkness in their hearts. That's okay, and we must learn to accept it, not cast it out.