Mori & Nori are two distinct personalities of a girl originally named Mono Ri. The girls currently reside in Veta Lake where they have their own quest. They are always trying to get rid of the other personality but neither succeed.
It is said that Mono Ri's parents were cursed into bearing a child for Maleria because she wanted one of her own. When The Oracle had a vision of her plan, Shinwa tried to cast a counter spell which didn't get rid of the curse but simply balanced it.
Mori and Nori are two different personalities of the same girl that control the girl's body at different times. At night (8pm Subeta time), Mori has control as she is the daughter of Maleria. During the daylight (6am Subeta time), Nori is in control as she is part of Shinwa's blessing.