Shikama Doji was one of the demons that had resided in Mahiru. When Shinoa was younger, Mahiru extracted Shikama Doji using unknown means in order to protect Shinoa from experimentation. Mahiru later gave Shikama Doji to Guren to give to Shinoa.
The human Shikama Doji formed a contract with. They have been together since prior to the manga story line in 2020. She appears to have been born with Shikama Doji residing inside her do to experimentation performed under Tenri Hīragi's command. Shinoa seems to be fond of Shikama Doji which can be seen by the way she fondly addresses Shikama Doji as "Shi-chan". Shikama doji states that Shinoa was successful in the experiment that Tenri conducted due to lack of desires that Shinoa has. Shinoa can contract to any number of demons without getting possessed by them, Shinoa is still unaware about this.