You can download, install, and play UNDECEMBER through the FLOOR PC Client & STEAM.

Download the client by pressing the Download button on the top menu of the FLOOR official website.

[Download FLOOR PC Client]

The downloaded file requires a separate installation process.
Run the client file to view the 'License Agreement', then set the required disk space and location to install the game.

In order to run the FLOOR PC Client, you must log in using a FLOOR Account. If you do not have an account, you can create one by visiting the home page using the 'Register' button.

Check the 'Remember ID' option when logging in to run the client using only your password in the future.

Check the 'Stay logged in' option to open the client while automatically logged in when running FLOOR.
(* We recommend you only use this option on your personal PC for security purposes.)

Run the FLOOR PC Client to view the list of games serviced by LINE GAMES that use the FLOOR PC Client.

Select UNDECEMBER and press the 'Install / Play' button to play the game.

If there is an update available, the game will be installed or updated first. You must press Play again once the update is complete.

Press ‘Install’ from STEAM’s UNDECEMBER page to install UNDECEMBER. After completing the installation, press ‘Play’ to launch the game client.

If there is an update available, the game will be updated first. You must press ‘Play’ again after completing the update.

[UNDECEMBER on Steam]