Hello! So I had this situation, where I go just next to the hot springs entrance/gate. My character change to swimsuit and sides of the screen become steamy (as it happens when you actually enter hot springs). Then I had this steamy border for some time until I actually entered hot springs.
#Hot springs steamy screen border bug
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pure flare
Hello Malwinis! Thank you for your report. Can you tell us the platform you use to play (Steam PC/Deck, Xbox PC/S/X, PlayStation 5) and your game version?
Also, do you happen to have any video capturing the issue? 😮
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Yes, sure! I'm playing on Steam PC, version v1.0-948. Here's a video but it's a day in the game so it is not dark enough to see that well, sorry about that. But I hope you can still see what I mean ^^ It happens when you move quickly right and left.
actually you can get rid of the steamy borders by just going to the fence again
pure flare
Thank you for sharing the video with us, Malwinis! Yes, I can see what you mean by the hot spring fog or steamy that remains there. 
Can you also share your save file so our team can take a closer look?
You can access it under this file path (make sure to unhide the AppData folder first) :
C:\Users\ <username>\AppData\Local\ProjectCoral\Saved\SaveGames (the .sav file)
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Thank you for sharing the video with us, Malwinis! Yes, I can see what you mean ...
of course!