If you grab the Mighty Gunvolt Burst demo on either 3DS or Switch, you can also net yourself the Ekoro character DLC for free. All you need to do is transfer your save data from the demo to the full game. Details on how to do that are below.
Ensure that the retail version is updated to the most recent version of the game.
Start up the retail game, while there is save data for the demo version on the system.
Choose the “DATA TRANSFER” option from the Title Screen.
Follow the instructions on-screen to select the save data from the demo version, then copy it to the file slot of the retail version.
In order for the transfer to work, you need to download the latest version of the game: Ver. 1.3. This update adds several new DLC characters: Ray, Copen, and Kurona. It also fixes a couple of issues for the game: you can find more details about it on this page!