@hakuma I have this problem too, but switching to ASDF instead of 1234 worked for me on these songs. When this problem occurs with 3 arrow keys as well you could try pressing 2 at the same time, releasing them and press the last one. Doing this really fast should work.
@Mokoan The pirate only appears on the 3x and 4x combo. The way to defeat him on pro is by pressing only one arrow or hold when you have to press two of them at the same time to make sure you don't go to 5x or 10x.
It would be really cool if you released some kind of editor to enable us to make custom songs. I was thinking about some program in which we can upload songs, place the notes on a timeline and share it with others after some testing. Also, 5/5 for this awesome game. :)
@MIchael 420 You can also draw the flag, a stereotype Japanese person, sushi, manga, Japanese like symbols or whatever you can come up with that is related to Japan. Just be creative, you don't have to draw the exact thing that the players have to guess.
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 "Post it Draw it"){kind=icon}
 "Sieger: Level Pack"){kind=icon}
 "Insectonator: Zombie mode"){kind=icon}
 "Balance Balls 2"){kind=icon}
 "Mad World"){kind=icon}
 "Cargo Bridge"){kind=icon}
 "Nano War"){kind=icon}
 "Super Crazy Guitar Maniac Deluxe 2"){kind=icon}