The name users of Wikimedia projects choose for themselves is not set in stone. Any steward or global renamer can change your username. You can only be renamed to an account that does not exist (using mw:Extension:Renameuser). Contact any global renamer and ask for instructions.
リクエストをSteward requests/Username changesに送信してください。
リクエストをSteward requests/Username changesに追加してください。
On request, stewards or global renamers can change user account settings and article histories such that all previous edits of a given user are attributed to the new name. This has been done several times in the past, either voluntarily, or forced according to the policy on offensive usernames on the English Wikipedia. Account deletion is not carried out on Wikimedia projects, so if you wish to become anonymous after making edits with your account, the way to achieve this is to change username.
When a name is changed, the previous account ceases to exist, and the user may immediately log in with the same password under the new name. The user may wish to re-create the old account to prevent impersonation. In the case of forced name changes, the old account will be recreated and then blocked. Signatures in talk pages can be changed manually if desired. The deletion log and the upload log are not altered.