Go for it! As far as I'm concerned, even the anime concept is still 100% yours and you still hold the copyright; you just let me borrow it for a while. It's still listed as by you in the credits. I'd have to triple check, but I'm even pretty sure yours is the only name listed for it under the credits. I only did joint credits with myself for any ideas I had to do a lot of fleshing out for, and I didn't need to come up with a lot storytelling-wise for Clockwork Under City Lights.