There are 2 ways:
A) you can either download the reworked AI version from a comment above
B) Or you can fullscreen with the app called Lossless Scaling. Guide:
Step 1.) Download the app:
Pixeldrain
Step 2.) Extract the folder from archive (extract 7zip or WinRar or something else)
Step 3.) Run Lossless Scalling.exe
Step 4.) On the right side in the pannel
"Scalling" change
"Type" to
"Anime4K". (default option is something like FSR and you change that)
Step 5.) Change
"Size" to
"Ultra Large". (This option is right under "Type" column.)
Step 6.) Start your game. (Agent Mirai)
Step 7.) Switch back to Lossless Scalling window and click on
"Scale" in the upper right corner. Now you have 5seconds to switch back to the game (Agent Mirai). After 5seconds the game will go to fullscreen with better graphics.
I prefer the app Lossless Scaling, because it works on all games. And the app improves the graphics.