I think Checkmate mentioned in his update that you can edit your username yourself once every 180. There is the option in settings > edit profile > edit username. Don't know, if it works, though.
Sorry, can you please look at my requests and tell if you have it? Thanks in advance.
https://www.anime-sharing.com/threads/request-211210-rj361498-tentacle-works-テンタクルワークス-賢者ちゃんとhな触手.1392118/
https://www.anime-sharing.com/threads/request-231104-rj01109498-takotubo-タコツボ-つくよヴィレッジ.1397470/
https://www.anime-sharing.com/threads/request-misotake-みそテイク-multiple-games.1404036/