thank you for your answer,unfortunately  I already knew about that and it doesnt give me full closure on what the key does

boi said:

You need to clear the level with 0 anger value and then enter a string of letters. For details, you can watch the video of "Lonely Note", or just press the keyboard, press every letter once, and a door will appear. Remember, Be sure to buy the ID card from Mr. Tomato first, otherwise you will be kicked out of the game. There is a useful information in it, which is the few sheets of paper in the cabinet, and the 2348 on the drawing board is also very useful.