Technically, all that a Kuei-jin must do to be an akuma is to have willing and knowing congress with a Yama King or his emissaries. Yet, as in all things, there are degrees. Even in the great uji of Japan, the influence of the lords of Yomi Wan is plain to see. Walking the nightmare-haunted sleep of the fallen Guan Ren, the Yama Kings and their minions tempt and torment. The lords of Yomi seek to spread suspicion, dissent and sedition among the ranks of the Wan Kuei, as well as to recruit pawns for their endless schemes in the Middle Kingdom. In furthering these goals, truth is as effective a weapon as lies, if not more so. Yet by ancient law, a Kuei-jin who pays heed to a Yama King's words, no matter to what end, would be considered one of the Devil-eaten.

Outside of wordplay and conversation, commerce with the Yama Kings is generally divided into three major categories by Kuei-jin legal scholars. The first category of commerce is called General or Lesser Commerce. This commerce is "lesser" only in that it does not involve the Kuei-jin's soul. Instead of a fragment of her soul, the Wan Kuei pays the Yama King in something of equivalent value - an artifact, important information about the doings of her court, or an eye carefully averted as the Yomi lord's minions go about their business in the Kuei-jin's demesne.

The next category of dealing with the Yama Kings is Soul Commerce, also called Iris Bulb Commerce because it splits up the Kuei-jin's soul as the gardener splits up iris bulbs when they are removed from the ground for the winter. In this form of commerce, the Kuei-jin enters into negotiations with a Yama King or his representative, usually by summoning them through the Ritual of the Black Peony. Though the Yama Kings occasionally approach prospective akuma themselves, they are as a rule uninterested in dealings with those who do not have the determination, resources and skill to perform the ritual. Thus, Iris Bulb Commerce is, by and large, the province of jina and mandarins. Only the most talented Running Monkeys will make it over the minimum competence bar, and even fewer of these souls are valuable enough for a lord of Yomi Wan to deign to negotiate directly.

The third form of commerce is total and unconditional subjection of the Kuei-jin's soul to the Yama Kings. Called the Pact of Ebony and Scarlet Jade, the transaction occurs when the akuma-to-be willingly offers his entire soul all at once. In order to undertake this rite, the Kuei-jin's soul must be entirely his own - the Yama Kings are not interested in damaged goods or slaves whose loyalties are divided (and have no doubts, self-inflicted slavery is indubitably the truth of the newly minted akuma's state). However, while the Ebony and Scarlet Jade akuma are unfree, bound even to their very highest souls into the webs of their demonic masters, their slavery is in many ways a most exalted state.