-----
Since Kireina's soul became Rank 5 and her soul mutated, she gained the power to control the residual souls that she had eaten.
In Genesis, the composition of the Soul is even more complex than on Earth, where it is only a single ethereal existence.
Thanks to the Soul Attribute, souls have different compositions, this is thanks to both Magic Energy and Life Energy, which after being absorbed by a Soul through their physical bodies, can create Soul Energy.
Soul Energy can be naturally generated by a Soul as their bodies keep living, and souls can naturally raise in their ranks as their physical bodies live for very long, but there are other methods to raise one's Soul Rank, that is by eating other Souls or nourishing one soul with different Psyche Nourishment Techniques.