Remmuh was an MAD contributor active from around January 2017 to August 2018.
They were very popular in the Cookie community for making high quality MAD, especially during 2017, and they were as much famous as the two of the representatives of the NND MAD community in 2017.
During February 2018, an alternative account of remmuh named "hummer" was found, but it didn't have as many views compared to the main account so remmuh got teased for it.
During July 2018, his Twitter account was frozen but while many people just recreated their accounts, he has since disappeared from Twitter completely.
Treatment on NicoNico
Since he used to use YW as his icon, he was depicted as Sagimaru in secondary works.
Later his icon was changed to child HSI wearing a hat, so he's sometimes depicted in that avatar.