A normie has wandered into a weeb game, i think you are lost, go here instead
Pretty sure he’s using one of the many different android emulating software available on pc with an app that forces games into landscape mode. Such as this.
I'm currently trying Nikke out on Bluestacks and Rotation Control seems to work fine locking the game in landscape mode.
I wish I could use LDPlayer, but I'm not about to give up Hyper-V & WSL2 on my desktop.
This is the one I saw a streamer planning on using, and has used on other games for his android.