You can change your in-game Nickname by using a [Rename Card]. You can obtain a [Rename Card] for free or purchase in the [SHOP].

1.You can obtain a [Rename Card] through Missions, Events for free.
-Completing the lv 3 and lv.10 Progress Missions to get a [Rename Card].
-Pay attention to other missions or events which may has a reward of [Rename Card] as of current or in the future.

2.You can purchase the [Rename Card] in the Shop.
-Go to [SHOP] -> [Treasures]. You can find the [Rename Card] in the list.

*You can only change your nickname once per day and the "Rename Card" will disappear from your account once used. You will have to obtain another one for further name changes.