I'm inclined at the moment to (and did) just mass edit them, and delete the artist entries for inaka and ika_(artist), so they don't come up in and thus confuse find artist/source searches/mass edit.
They're too simple and potentially ambiguous - and thus "valuable" - to have tied up in aliases. I expect there's a very good chance that there are artists out there we'll add one day using those names. Better to have the tags available in that case.
So everything is under ica now.