https://commons.wikimedia.org/w/index.php?title=Special%3ALog&type=move&page=File%3AFlag_of_the_Republic_of_Ezo.svg
http://archive.is/nu1qv
And removed from the enwiki article:
https://en.wikipedia.org/w/index.php?title=Republic_of_Ezo&diff=717422809
Viewing the talk page of both the image and the article, it's pretty clear that the Wikipedians known about the issue for years:
http://archive.is/xLogI
https://en.wikipedia.org/wiki/Talk:Republic_of_Ezo#Source_of_Flag.3F_.28Republic_of_Ezo.29
Zscout370 asserted that the flag exists as merchandise or something but then made a "Well, from reading it more,..." statement, suggesting that he didn't have any clue about what he was talking about when he made his first statement.
In fact, Zscout370 had deleted the flag during the previous year but decided to restore it for some reason:It's fake, but still enjoys a mythical status in Japan as a flag and can be purchased there. [[User:Zscout370]] <sup>[[User_talk:Zscout370|(Return fire)]]</sup> 16:09, 28 May 2010 (UTC)
:Well, from reading it more, it is more of wether not a flag exists but what are my sources for the design. There was a JPEG image of the flag on the English Wikipedia, and I just made a vector of that. [[User:Zscout370]] <sup>[[User_talk:Zscout370|(Return fire)]]</sup> 16:14, 28 May 2010 (UTC)
https://commons.wikimedia.org/w/index.php?title=Special%3ALog&type=delete&page=File%3AFlag_of_the_Republic_of_Ezo.svg
I decided to find the source of the flag. Zscout370 uploaded "Flag_of_the_Republic_of_Ezo.svg" onto enwiki in 2008 in order to replace "EzoFlag.jpg":16:17, 28 May 2010 Zscout370 (talk | contribs) restored page File:Flag of the Republic of Ezo.svg (4 revisions and 1 file restored)
02:10, 26 July 2009 Zscout370 (talk | contribs) deleted page File:Flag of the Republic of Ezo.svg (Author request: yall are right, this is a fantasy flag, based on information I found in Japan)
https://en.wikipedia.org/w/index.php?title=Special:Log&offset=20080109000000&limit=03&type=&user=Zscout370
Kintetsubuffalo uploaded "EzoFlag.jpg" in 2007 in order to replace "Ezo_flag.gif":
https://en.wikipedia.org/w/index.php?title=Special%3ALog&page=File%3AEzoFlag.jpg
Goustien copied "Ezo_flag.gif" from the Ill Bethisad wiki, an alternate history project:
https://en.wikipedia.org/w/index.php?title=Special%3ALog&page=File%3AEzo_flag.gif
Nik created the flag in 2007 in order to replace his or her previous 2005 design:05:02, 13 October 2007 Goustien (talk | contribs) uploaded File:Ezo flag.gif (Copied from the Wiki page http://ib.frath.net/w/Ezo)
http://ib.frath.net/w/File:Ezo_flag.gif
Now get this: The design of the flag is simply "SNORist Republic of Ezo" flag (another one of Nik's fictional creations) combined with the Japanese Imperial Chrysanthemum, so half of the flag doesn't have anything to do with the emblems used by historical Japan. Contrary to what Zscout370 claimed, this flag can't possibly have been sold as merchandise in Japanese shops (unless it was a reaction to what was in the Wikipedia article). This also means that the second portion of Zscout370's "this is a fantasy flag, based on information I found in Japan" statement is completely false. He didn't "find information in Japan"; he merely made a SVG version of an image someone else uploaded to Wikipedia.
The flag was been used on the enwiki article in one form or another from October 2007 to April 2016 (eight and a half years). This also makes Zscout370, a former global sysop, one of the highest-ranking hoaxers in Wikipedia's history. To quote EricBarbour:
http://wikipediocracy.com/forum/viewtopic.php?p=111772#p111772