To become a member of an NPC Subpath, you need Ox Karma or above. You must have become a Dog linguist. Go to Baek in the scroll shop in the north west corner of kugnae, and say your path's totem god's name to him (Baekho for Rogues, Ju jak for Mages, Hyun moo for Poets, Chung Ryong for Warriors)
After this, go to Buya, and go above the North gate and west until you find a tree and a place with a lot of rabbits. Walk around until you get a popup that says you see a rabbit and it smiles at you. Make sure he smiles, otherwise you need more karma. Go to the Dog that teaches you your spells (Warrior Dog = Kug fox cave, Mage dog = Kugnae Taverns, Rogue dog = Buya fox cave, Poet dog = Watcher Tree), say Secret to them, and choose yes.
Next, go back to Baek and say your totem god again, he will ask for a couple items. 1 Mythic Favor, 10 Splendid Tiger pelts, and 1bil xp (1,000,000,000) say your totem god again ONLY IF YOU HAVE ALL THE THINGS OTHERWISE YOU LOSE STUFF AND ITS NOT FUN
After you give him the required things he will make you your NPC subpath.
To leave the NPC Subpath, say Cleanse to your Dog, and they will remove you but you lose Karma.