I'll have something done for this soon. I have an idea of what Master I'll use, or rather reuse, for this. But, I'm still deciding between a canon Servant or not.
So demons are obligate man-eaters? I don’t suppose they could survive off other demons or animals or something. Okay, let me make amendments.
He may have been more conceptual at birth, but has since become a regular devil. He is now so closely linked to his human body that he cannot leave it without some kind of exorcism. If the body dies by natural means, he will remain, trapped in the corpse until some supernatural force like a demon or a devil hunter kills him, or he starves to death. And if he were ejected from the body, he would be something like a ghost, with a defined spiritual form open to attack.
As for the barriers. Each barrier is anchored to a reference location, either himself or a massive body like the Earth. If a particle hits a barrier that it cannot pass through, it will reflect off elastically. His barriers offer zero protection against spiritual or magical attacks, and hold up poorly in the face of such supernatural things. A blessed pebble would pass through and destroy a barrier without shifting in trajectory, but an artillery shell would just ricochet. In other words, someone shanking him from behind with the right knife is more of a threat than launching him into the Sun.
Using the barriers offensively is possible by placing one in front of someone moving too fast to brake. But a barrier will be stopped upon contact with a stationary solid because of the lack of motion in the solid, so it cannot be used like a sword. As for non-combat uses, he can split molecules and atoms apart, and assemble complex structures atom-by-atom over a very long span of time using elements in the environment.
The upper limit in size is around that of a domed stadium for a single contiguous barrier, which is very taxing to maintain for more than a minute. He can also make numerous minuscule barriers, even at sizes not visible to the human eye, but the smaller and more intricate the barriers are, the harder it is to maintain. Barriers the size of human cells would only be able to cover a small door at most. Also, he can only create barriers within his field of vision or around his body, though he can maintain them without looking.
I will tone things down if need be.
A few more questions. How are the usual international relations or transfers between DHA branches? I get that various hunters are being sent to Japan because of an emergency (or a developing unusual situation), but are there regular international missions too? If one moves to live elsewhere do they join that country's branch while they reside there?
I forgot to ask this before, but are there enchantments which conceal unusual hunting items (e.g. firearms in Japan would stand out) from mundane people? How widespread is the knowledge about devils among people who have nothing to do with the DHA in any case (does the government know and cooperate)? Do hunters have the cover of being 'special agents' so they can get access to places or have authority over regular people in certain situations, for example if they need to access/evacuate a building?
Greetings, is this still open for players?
Would a Youkai that doesn't particularly want to hurt anyone be acceptable? I was thinking of a ghost that mostly makes a nuisance of herself and enjoys scaring Humans. More of a trickster than a threat.