Kyouhei Oikawa/Zafkiel

Zafkiel (ザフキエル Zafukieru) is the Darkness Spirit of Akasha and the fourth to arrived in the "real" world. She is infamously known by other spirits as the most brutal and the second strongest behind Ragnarok. Not only that, she is known for be very deceiving and manipulating, even attempted to betray Ragnarok multiple times.

She is the sixth spirit to be sealed and is currently wielded by Kyouhei Oikawa, whom she took a liking for and is very aroused whenever she is around him, much to Kyouhei and Roku's dismay. Zafkiel, while in the "real" world, took upon the human name Erika Tokisaki (時崎・エリカ Tokizaki Erika) and is known as the Shadows of Nightmare (悪夢の影, Akumu no Kage) by Necessarius.

Personality
Sandalphon/Himeka stated that it's very hard to describe Zafkiel/Erika's personality because of her secondary powers, which is the ability to control time and create multiple copies of herself from different points of time. Which is true since Zafkiel can appear as a normal high school girl with a girlish personality at one time while at another time appears to be a psychopathic killer. Although, she does not have multiple personalities but she can have multiple pasts due to her powers. Zafkiel also stated that no other Akasha Spirit knew her "true" personality except for Ratatosk; who is the only person capable of understanding about her.

Although, despite her rather brutal demeanor and manipulative nature, Zafkiel herself is not entirely evil. This can be shown that all of her victims are those who commits sin and must be "punished" by her statement, most notably ones who mistreated their Pokémon; the only things that maintains Zafkiel's sanity from going too far gone. Zafkiel also shows good sides to the rest of the spirits and despite her numerous attempts at treachery, is very loyal to Ratatosk; who also shows respect for her as well.

Probably, Zafkiel's most notable aspect of her personality is that of her liking to whoever was her wielder, in this case: Kyouhei. She is shown to have a rather aspect of affection for him and shows several attitudes of a yandere character, which is a good reason on why Kyouhei has rights of being scared for her and the subject of her getting numerous beatings out from Roku.

Spirit Powers
Akashic Records (アカシックレコード, Akashikkurekōdo):

Nox Nyctores
Diabolus Horologium - Lilith (悪魔の時計・リリス, Akuma no Tokei: Ririsu lit. Devil's Clock: Lilith):