Get the highest score in Zoo Keeper, Tokoton 100, Quest and Time Attack modes.
Hitting the 'ILLUSION' bonus will score you '1500000' points.
Basically if you're ultra skilful and with a bit of luck this is possible to do. First you have to get 3 blinking tiles on the screen; next you must connect all three in a row, horizontal or vertical. After it's been connected, the screen will flash with a spark bursting out and the word 'ILLUSION - 1500000' in the centre of the screen.
If you're fast enough with the stylus, you can score chains even when the falling tiles don't line up as they fall - just make another move while the tiles are settling, and as long as you're not trying to move a tile which hasn't fallen yet, it'll be counted as part of the move.
Unlockable 4th difficulty, "gekimuzu".
To obtain a 4th difficulty, you need to get the highscore on
all 4 modes of gameplay.
Zoo keeper: 1200000+ points needed.
Tokoton 100: 1800000+ points needed.
Quest mode: 10000+ Yen needed.
Time attack: 600000+ points needed.
After getting all 4 high scores, a 4th difficulty appears in the top line of the option menu.
This difficulty means "Expert" or literally "difficult-player" and has a huge advantage of doubling all the normal points you achieve.