mochi

Clicking the full entry wiki link on this tag leads to an artist page going by the same name, and giving the posts results you expect from the general tag mochi is.

There's apparently no post wrongly using this tag, which would then belong to the said artist.
The artist page itself pretty much looks like it was created by mistake.

I suppose it should be deleted?

I would, but artist entries can't be deleted now, only deactivated. Maybe albert has the ability to delete them (though it'd be good if I did too).