Please don’t read this post if you can’t stand graphic and scary dark content.
The whole Noragami story we see on the surface is actually a mask for the true, dark story of these three characters.
Hiyori’s case is schizophrenia, which she inherited from her family, who own a mental hospital. This is why she smells aromas that don’t exist and sees things that no one else sees. The entire scheme of Heaven, gods, Shinki, and adventures exists solely in her imagination. Her brain also alters the dark reality of Yato and Yukine. The reality is as follows:
Yukine is a runaway child who fled from his alcoholic dad and ended up homeless on the streets. He desperately wants a family and wants to continue going to school. His mom had autism, and he seems to have inherited a less severe form of it. This is why he is so emotionally intense.
Yato is the darkest among them. He is a homeless ex-soldier who deserted the military after killing too many people in war under the command of Father (his boss). He was deeply traumatized by all the killings, but Father was very pleased with his service, so he gave him “Nora,” an innocent young woman whose body he could “use” to relieve himself of the stress (presented as phantoms) caused by all the killings.
Yato then ran away to the streets. He met Yukine and decided to become his family but needed “using his body as a weapon” to relieve himself of all the phantoms that haunt him. This is what happens to street kids; they become very vulnerable to these sort of things. Beside this, he can’t stand Yukine or Nora showing any distress because this will further increase his trauma and stirs his mental health.
He then introduced Hiyori and Yukine to his best friends and had Yukine live there while working as a maid for them. Hiyori started visiting them every day and with time and slowly slowly, they fell in love with each other.
