You can only delete characters at Level 60 or above,

and this can be done by selecting Delete in the bottom left corner of the Character Selection screen.

Deletion is subject to a 7-day grace period and can be canceled within that period.

After the 7-day grace period has elapsed, the character will be deleted and can't be restored.

※ Deleting your character will delete all of your items, so be sure to check them beforehand.

※ Also, certain items prevent character deletion once obtained. You must delete these items before deleting your character.