Unfortunately I built the game for 16:9 or wider screen ratios, whereas yours is 5:4. And I currently don't have a 'change ratio' option in the game. (I will try to add one for Version 1 of the game)
For now, you can go to your computer's Settings > System > Display then click on display resolution and change it to 1920x1080. Your screen will be a bit stretched, but you will be able to see Starla and the monster girls for the time being