owl＊tree has acknowledged the video at least through the following tweets: "Wow" (https://twitter.com/owltree_pvq/status/1386188649650294784) & "WTF!! 700,000 views Over!?" (https://twitter.com/owltree_pvq/status/1422191103957082118)
The arranger of Shuric Scan has acknowledged this video at least through the following YouTube comment (https://www.youtube.com/watch?v=3x8jlCz0jw0&lc=UgwtukkkqzM7xZDrPEd4AaABAg.9b8PeGipCsx9gYoSWC8IQd): "Truth: 1. I made a cover of Ninja Gaiden II OST for TSRh team. 2. tPORt team used it in Shuric Scan keygen. 3. tomgoodmen created his video "manwith10scans" based on my cover."
I assume the Niconico URL (https://web.archive.org/web/20210228124052/https://www.nicovideo.jp/watch/sm15516751) to be correct based on the matching title (See here: https://twitter.com/hashtag/sm15516751) and length as well as tags mentioning Zen, stein and Animal Crossing.
Twitter results related to the original Niconico upload (https://twitter.com/hashtag/sm15988513) imply that the video was originally titled "AND" before being renamed to "FUN藤さん" later on.
10. [YTPMV] Holy Perplexity, Batman!: A couple of old tweets (https://twitter.com/ouh80hwr/status/20458198273 & https://twitter.com/rcatstott/status/340705963730432000) link to a YouTube video by this name (https://www.youtube.com/watch?v=BWudvvfLuyI), but no archives seem to exist to provide information regarding its creator or upload date. The earliest tweet implies that it was around by 2010/08/06.
An archived page of Mestre3224's channel from 2011/07/05 (https://web.archive.org/web/20110705100808/http://www.youtube.com/user/Mestre3224) shows that the video's original title was "YTPMVBR - 1300 Subs" and its original ID was "3LlXiPWwfaY". Its original video page has not been archived. It was originally uploaded sometime between 2011/05/11-05/17, based on the video uploaded just prior to it (https://web.archive.org/web/20111027045559/http://www.youtube.com/watch?v=RqA8maJ2Jxo) and a tweet linking it (https://twitter.com/sweetdreams1993/status/70385845173104640).
While I can confirm that user/118374604 was named 手ブラ at one point, the name's general-ness leaves it uncertain whether or not user/132656764 is the exact same user. There's a choice to split the two channels in two tags if it remains uncertain enough.
The URL for the original video (https://youtube.com/watch?v=mVqJZ8tl93g) stems from one of the surviving part uploads (https://www.youtube.com/watch?v=_YYXkZ2QI5o) that links the collab as well as two Twitter posts linking it and mentioning it by name (https://x.com/Sunsoft5A/status/400145795686891521 & https://x.com/Handlerdb/status/489193712279244800). The upload date stems from a personal download of the original upload, which labels its encoded and tagged date as "2013-07-01 01:29:49 UTC". A comment thread on the reupload of the collab (https://www.youtube.com/watch?v=pB-qNkQWetY&lc=UgxD42ApcxmLZnEsNlN4AaABAg) recounts the following participant list:
1. ZeFrenchTopHat,
2. Jab50Yen,
3. pelz,
4. Smelku (?),
5. Kawaiidesunigga,
6. Zillah,
7. Ray Hamilton/Hamarejun,
8. NewSpIcington/ytpguy,
9. TheBigEth,
10. spiltlevelemergency,
11. Smashi &
12. yopox
The URL, upload date and description of the original YouTube upload (https://youtube.com/watch?v=8atzh3k5xQo) was taken from an archive that no longer seems to be online: http://www.mefeedia.com/watch/42002901