I hadn't realized it, but I think I may have the same issue since there is nothing in the top right corner, even when the game says there should be. I did not see anything to interact with, so it just ended with me losing all my sanity without making any choices.
The top right corner thing mentioned in dialog is a UI reminder work as a hint about dragging on the screen to pan the CG. Then I found out the reminder is not an actual UI thus is not showing on the screen.
At this version, you can click on the flying Sanity Word to slower the sanity reducing. Most of the Sanity Word will die after 1 click. Using this control the sanity is at the level that you desired.
Oh, I didn't know you could click on the words. I guess I don't really understand what genre this game is. It says Visual Novel, but it feels a lot more like a survival game.
Oh, that's okay.
Thinking the whole game will be a baby between the ending credit (and only an inspiration, not the actual shooting vibe) of Nier Automata and Phoenix Wright. The version now is a fraction about the mechanism, at the most scenario, detective gone crazy or die is not happen that much.
Here is the ending credit I mentioned before.