It's not selfcest... it's just masturbation with style!
You see, selfcest is when two different versions of the same character have sex.
But Youmu is half-human, half-ghost: both parts are Youmu, they are not two separate versions, is only one version. So she is sexually auto-stimulating herself, using a part of herself; is not very different than if she was using her finger.
Instead of fingering herself, she is ghosting herself. ;)
While we're on the topic of tags, should futanari or at least implied_futanari be added to this? Unless of course Youmu's ghost half is male in this picture.
Well, most images of Youmu with the selfcest tag are wrong. I don't think janitors would want to change all of them. (but IMHO I think they should, besides, there are not a lot of them)
BTW, here is an actually correct tagged selfcest image of Youmu. This one show what is Youmu having selfcest : post #823388
