The following list of account names that are near completely confirmed to be owned by koronba.

- ころんば	(Koronba)			(september 2008 - march 2016)
- 楽観主義 	(Rakkan Shugi)		(september 2012 - december 2014)
- 2号. 		(2gou.)				(november 2011 - march 2016)
- MARK.3	(MARK.3) [3gou.]	(april 2013 - june 2013)
- Speder2	(Speder2)			(february 2014 - march 2016)
- 155		(155)				(september 2014 - september 2014)
- こてむそ	(Kotemusob)			(january 2013 - march 2016)



This list of names being refered to as Koronba has been known about in the japanese community since at least around the time that Koronba was still active. However the exact origins of the list of accounts is unknown, it dates back to some time between september 2014 and march 2016, with most of the information related to it having been deleted. Source: https://uboachan.net/fg/res/7735.html#q11947 (This is the oldest individual example I could find, but there are many references to the rumors being much older.)

It may have been posted by Koronba himself on either of his twitter accounts while they were active around ~2013 (nnn_koronba or stade_002). Or it may have also been leaked by someone that Koronba was close to and posted onto some now-deleted japanese webforum, or something similar.

To start, the following is definitive proof that 2号. and Koronba are the same person:

	https://web.archive.org/web/20100922035841/http://www.nicovideo.jp:80/watch/sm12084498

In this video, 2号. included a dropbox url to download a song he created. (http://dl.dropbox.com/u/5448275/LiquidHANNYAfunk.mp3)
Going by the username in the link (5448275), it matches perfectly to nnn_koronba's dropbox number, found in a retweet to one of his now deleted tweets (http://web.archive.org/web/20201230112952/https://twitter.com/GugenTV/status/26184187583).
Proving that 2号. and Koronba shared the same dropbox account, and are indeed the same person.
This proof was not known to anyone until the beginning of 2019, a long period of time after the list of names was circulating. (This date is confirmed as I spoke to the person who discovered to proof originally.)

It's very safe to say that MARK.3 and 楽観主義 are 2号.'s alternate accounts, making videos in the same style and having no online presence whatsoever aside from posting to their respective channels.
With MARK. 3, it's relatively obvious from the word play of 2号 translating to mark. 2, as well as the use of 2gou-esque backgrounds in all their videos that it is an alt project that lasted 3 months, and served as a side series.
楽観主義's connection seems to be that it was 2号.'s side channel for posting videos that Koronba was not proud enough of, or didn't fit well enough to go on the main channel, since all otomads and remixes posted to the channel barely or moved, and seemed like slightly lower effort content compared to the 2号. uploads.

Comparing speder2's progression of musical ability against what was uploaded to the 2号. and ころんば accounts shows an extreme amount of similarities going from timepoint to timepoint.
Similarly, when comparing the dates of 死霊マンレッド comics uploaded by Koronba alongside kotemusob's art from identical time periods shows striking similarities in the style and artistic abilities at that time.
When comparing the dates of content uploaded based against their quality, this pattern is very visible throught each of the accounts (speder2's first compositions are extremely good, meaning they had to have had uploaded music somewhere else beforehand).

Other details include:
- Consecutive numbering scheme on private file names is the same between Koronba and Speder2. (http://web.archive.org/web/20201230142850/https://imgur.com/a/3VT80hp)
- Twitter user who knew kotemusob referring to him as Koronba (http://web.archive.org/web/20201230142636/https://twitter.com/raimukunb/status/1229183528958648322) [Raimukun - Omairi Original song by ころんば (a.k.a こてむそ) - お参り Genre : LoFi たとえ足りない曲でもこの方のために捧げます。 FULL : https://soundcloud.com/channel-thenewlimee/iriamo 原曲 : https://pixiv.net/artworks/54170142]
- Every account dissapearing in march of 2016, coinciding with Koronba's disappearance.

Going off of these facts alone, and the fact that it's origins have all been deleted, gives great reason to believe that all names given in the list are Koronba's accounts.
Another reason to add to it's credibility is the sheer obscurity of all these accounts. It woudln't make any sense to connect the accounts such as 楽観主義, 2号., and MARK.3 to the ころんば account without an extremely meaningful reason, seeing as their styles are all polar opposites to ころんば.
It also would not make sense for this list to only be a rumor since as it originated far before Koronba's mass boost in popularity. And out of context, the list of accounts seems almost completely random, IE: there would be no reason to suspect them without the pretext of them being related, seeing as many of these accounts such as kotemusob and 155 are extremely obscure.
What I mean by all this is that the list being created solely as a rumor by accounts having similar styles is out of the question, leavin the only plausible other explanation be that the list is in fact legitimiate.
This is further reinforced by the fact that the 2号. connection was only proven a long time after the original list was conceived.

Because of all this it can be assumed that ころんば, 楽観主義, MARK.3, Speder2, 155, こてむそ	, and 2号. are the same person.
If you see an active account claiming to be Koronba, or just has a similar style, they are most likely imitations inspired by Koronba's work and not actually him.