Basically what Kansa said. Your video isn't uploaded here, it's uploaded at Youtube. This site just has a feed to Youtube and displays videos posted to Youtube here, usually bringing up hits for anime related videos first.
So if you delete the video from Youtube, it wouldn't appear here anymore, etc. If it's a problem, something could possibly be done about it, but nobody has taken your video and uploaded it here. It's about the same as someone embedding your videos on a site with the link Youtube gives, I think.
ETA: I looked up your videos, and that's what it is. If you double click on the video screen, it takes you to the Youtube page you've hosted it on.