do we actually have any proof of its existence?

I've been thinking and searching for some time if we even have any proof of its existence, the only thing I could think of its that one screenshot of it being listed on some website which is probably fake. there is actually no way of even knowing if it was only 1 episode or maybe much more, or if even the original OP saw the whole thing because he said there were no credits so it might been cut. I've been also thinking about one thing that might help us get to the bottom of its existence, what if the series has an manga we weren't able to find yet sometimes when manga gets an anime adaptation they change the name a bit so it might be a good idea to try looking for manga which a similar story