The creator himself said he confirmed that he does not have it, apart from that, according to what a Spanish-speaking commentator sent, the following is known:
Greetings, to add.
There is a Japanese mugen database that has the following referenced about madotsuki
https://pastebin.com/ExywnP7xIn the threads that are archived from 4 ch to n on the video game board. There are several anons who mention that they have found strange characters (they demonstrate this with a webm or by posting the links if they are asked) and mentioning that they find them by searching purely in Japanese.
Searching as mugen+[character name in Japanese] on niconicoduoga was also mentioned. But in this case it won't work because of what was mentioned in your video.
I can think of several ways to find the character
IBS (f u t u b a chan, where the mugen full game Nijikaku came out) and Japanese forums (the latter focused on mugen)
Users who commented on eiten's madotsuki video
Other people you interact with on your social networks about mugen
It could also be that it is uploaded on b a i d u, I think the b a i d u search engine no longer works but you need to check.
The IBS options will need to speak Japanese and in forums it is likely yes or no like niconicoduoga users or people related to mugen with eiten.
I hope you have new information about madotsuki.
P.S. Youtube gave me a lot of trouble posting this.
