You've won a Mansion![edit]
As the game begins, Luigi is walking through the dark woods with his flashlight, following the directions of an infinitely more cheerful map to a large, spooky mansion. Apparently this is a prize he won in a competition he can't remember entering. He opens the door, but there is no answer. Mario left long before him, so he should be there by now. But this is Luigi's mansion, so he enters anyway.
When you first enter the mansion’s Foyer, go up the stairs to the left or right of you. Do not try to open the glowing double door in front of you. When you reach the top of the stairs, try the double doors immediately in front of you. They will be locked. After you try it once, you will hear an odd noise coming from the bottom of the stairs. Go down the staircase, and you will see a cut-scene of a ghost entering the room upstairs, and dropping a key along the way. Pick up the key, and try the double doors upstairs again. It should open.
Once inside, Luigi will walk in nervously, and a ghost will appear from nowhere and try to attack Luigi! But equally as suddenly, a small old man will come and try to suck up the ghost. But the ghost is too strong, and escapes. Luigi will go to help the man, but three more ghosts will appear, and the two men run out of the mansion.
Professor E. Gadd and the Poltergust 3000[edit]
The man will introduce himself as Professor Elvin Gadd, and the area you are in now as his Laboratory. He believes that the Mansion and the competition Luigi 'won' it in are all very suspicious. The Professor explains that the Mansion appeared overnight just a few days ago. He then mentions a small fellow dressed in red who went into the Mansion, and never came out. The Professor is horrified to discover that this is actually Luigi's brother, Mario, and decides that he will help Luigi defeat the ghosts and save Mario.
The next screen allows you to choose your controller scheme. Once you're happy with your choice, press 
to continue to the Training Room. Luigi now carries Professor E. Gadd's invention, the Poltergust 3000, on his back. This powerful vacuum can suck up the ghosts. The Professor will explain how to operate it, and give you a couple of seconds to try it out. Now it's time to begin training. The Professor will explain that you need to stun them with your flashlight, then suck them up once they are stunned. The best method is to turn off your flashlight by holding 
, then facing the ghost and releasing . Once their heart appears, that's your chance! Ten ghosts will appear from the circular sections on the floor. After this, the Professor will ask you if you want to look around in his Gallery. If you accept, you'll go there. If not, you'll go back to the Lab.
In the Gallery, all of the paintings are gone, and only their frames and two large statues remain. The Professor will explain how to use your Game Boy Horror's first-person view. You can use this to check out almost anything of interest. For now, stick to third-person view and check the two angel statues by approaching them, and pressing . Once you've done this, you can talk to the Professor and return to the Lab. In the Lab, you can choose to go to the Mansion, the Training Room, or the Gallery. You can go to the Training Room if you feel you need to hone your skills. Once you're feeling courageous enough, head for the Mansion!