Currently, in addition to the main Japanese version, “Midnight Syndrome” is available in Chinese (Simplified), Korean, and Portuguese (Brazilian) versions.
The data should have been updated so that the game can be played on Steam, but we have confirmed a phenomenon where the language is not changed. This is due to my lack of skill and understanding.
But there is a solution. It requires several steps.

Enter the following command in the game Properties > Launch Options (the first part will vary depending on the installation path of the player) (see figure):.
F:\SteamLibrary\steamapps\common\MidnightSyndrome\MidnightSyndrome_SC(this part will vary depending on the language you choose)\Game_boxed.exe” %command%.

This procedure seems to solve the problem. (Someone who can help me with this told me this...)

I apologize for the trouble I have caused to international players who wanted to play my game.

If that does not solve the problem, you can download a translated version at the following link.
https://midnight-games.booth.pm/items/5617529