References and other interesting things about the manga that one might miss on first glance.

Chapter 6 - Yorishige's Poem

「野辺に住む獣我に縁なくは憂かりし闇になほ迷はまし」
The poem that Yorishige recites here is taken from the Shintoshu, a collection of stories about Japanese gods written in the 14th century, and more specifically from the Suwa Engi Koto.

Chapter 69 - Unusual Weapons

Left: The Seven-Branched Sword (七支刀, Shichishitō), a famous weapon that is believed to have originated in Korea before being given as a gift to a Japanese ruler during the Yamato period.
Middle: An example of a dakouken (蛇行剣), a ceremonial sword with a blade that curves back and forth like a snake.
Right: Reminiscent of a douka (銅戈), bronze weapons based on the Chinese ge or dagger-axe. They were likely used for ritual reasons rather than actual combat.

Chapter 107 - Yorishige's White Hair

Yorishige's hair turns white as he is drained of his divine power. This is very similar to a scene in Matsui's debut work, Majin Tantei Nougami Neuro, in which the demon Neuro's hair turns white when he runs out of demonic power.