Habarudo said:
This is called T光 (透過光) in Japanese.
It has less to do with "sakuga" and is more of a compositing thing, so I'm unsure if it's something that would apply to this booru, but I think it's an interesting thought.
I agree. More composition-focused than animation but that could apply to background tags as well. Would be a nice touch to have as a tag though.