In the tutorial of the game, when you open the chest with the key you can't move or do anything anymore, no text box shows up, you can't pick up the key, and you can't walk, hell you can't open a menu, all i seem to be able to do is alt+F4 to quit the game.
Ran into this too, fortunately it's very easy to get a hang of the game.
Keys or right mouse to move, moving into an enemy damages them.
Left mouse to interact (pick up stuff, talk to/fuck NPCs and enemies).
The rest is just crawling through the dungeon and learning as you go.
Fucking an enemy (right click, hit the option) raises your cum meter but stuns/charms them for a while.
If your cum meter maxes out you lose, if you lose all your HP you lose.
You can masturbate to reduce your cum meter but it takes Mana.
Oh and you can pick up equipment, scrolls, and potions but sometimes they're cursed or have detrimental effects.