A brief observational note from a previous Kaijin Lord.
Despite the way they act, and the way they carry themselves, Kaijin technically don't have souls. At least, not in the same way aether warriors do.
This is evident by the fact that Kaijin are unable to manifest any of the key abilities that make aether warriors what they are.
One could argue that their innate forms count as a permanent [Regalia], but their inability to summon an [Astra], an [Icon], or an [Avatar] goes against that logic.
Then again, their ability to distort and upgrade these abilities in mortal warriors lends itself to the idea that kaijin don't have souls because they are souls.
But this does lead me to wonder something.
If a Kaijin had the ability to manifest such things, how would it look?
