I'm looking at the art here:
And some of the pictures seem to be the same as those by pon_(cielo), except slightly darker. However, pon_(cielo) seems to have deleted their Pixiv account so I can't check if it's a case of plagiarism or someone closing their account and reopening it under another name.
For the time being, I'm treating it as a separate artist under tamaxkake. If it turns out they are the same person we could alias them.
Updated by RaisingK