Completing your double dates with each of the characters successfully throughout the game will unlock the end scene, where you can see the romance art between them. It requires two successful double dates per pairing to unlock them, and there are 25 of them to collect, including the tutorial mission’s art. However, once you have collected them, you can’t go to the pause menu to find them. Romance art can only be found within the current save file. If you want to view previously unlocked gallery art of the characters, you need to head to the hotel where Kyu the love fairy is located.
Here, you can rest up to allow characters to gain back stamina, check on your progress, and the final option should allow you to check the gallery.
This will show you all of the pictures that you have previously unlocked. What you will see depends on the setting that you are currently using for the Censorship options. If you are playing a censored version of the game, you will only see these pictures.
However, if you have the censorship option turned off, you will see your currently selected option for viewing the artwork. If you enter one of the photos, you can cycle between the three options for how you view the artwork at your leisure.