You may have heard about the glitch regarding the Manual in Ten Desires from the touhou wiki. It mentions there that if you open the Manual 15 or more times, and then you go and select a difficulty and after that return to the difficulty screen, you will be met with a garbled up text. If you select that text and proceed to start the game, you will be playing the Extra stage on Hard difficulty, except there are no enemies and nothing else happens.
I've tested this myself and I would like to add few more things which are currently not mentioned there. Upon selecting the garbled text, it will turn into "Lunatic Mode", although neither the stage location or the difficulty shown in the upper corner are related to Lunatic. When you launch this bugged stage at first you are capable of shooting and bombing, but as soon as you kill an invisible enemy you will stop being able to do anything else than fly around. You will even lose the ability to focus. Also, the Point Value meter will show 500,000 instead of the regular 20,000 as in a regular Extra stage.
If you do the Manual glitch and choose Extra Start instead of Game Start, when you go back to the difficulty screen before choosing a character, the difficulty will be gone, showing nothing on the screen. However if you proceed to play it, it will just be a regular Extra stage.
Returning now to the ghostly "Lunatic Mode" text, it will persist on the Menu screen even if you return to the main menu. One thing to notice is that once the Manual glitch is active, even if you didn't trigger the garbled up text yet and you try to go back to the main menu, the Manual option would be selected instead of Game Start. Also, sometimes when trying to get the garbled up text you will land on Easy Mode when you go back, even if you never selected Easy when messing around.