It is a large black youkai was chasing Natsume for food.
Appearance[]
He wore white mask and traditional kimono in black, hence the name. He was a big youkai compared to the other youkai.
Plot[]
Knowing Natsume's the owner of Book of Friends, he wanted to consume Natsume. However, Natsume managed to avoid him by hiding on top of a tree.
Later on, when Natsume and Nyanko sensei were talking with Aokuchinashi, somehow the large black youkai found Natsume and sneaked attack on Natsume. He managed to bit Natsume's left hand before being banished by Nyanko-sensei.