Here's a little help for people who want to try, but can't understand Japanese:
Controls
W-D for red and white respectively.
A-S to dress and undress.
Basic Rules
Follow instructions on top.
If you get it wrong, the miss counter increases.
Miss counter topping out is a loss.
Tap any giant floating hearts to gain extra points.
Important Rules
Do not lower a flag if the game doesn't tell you to.
Some instructions aren't about the flags.
Examples: "Don't wear X", "Double Peace Sign"
After a non-flag instruction, do whatever you were doing before, and continue from there.
Flag Instructions
赤 ・ 白: Red / White
* Pay attention to the character. The color-coding tricks you sometimes
上げて ・ 上げる ・ あげる: Raise flag
上げたまま ・ 上げながら: Raise flag
下げて ・ 下げる ・ さげる: Lower flag
下げたまま ・ 下げながら: Lower flag
上げないで ・ 上げずに: Don't raise (Lower)
下げないで ・ 下げずに: Don't lower (Raise)
上げなくてはだめ: Raise flag
下げなくてはだめ: Lower flag
◯だけ上げる: Only raise this flag
◯だけ下げる: Only lower this flag (raise the other one)
Non-Flag Instructions
全部・何も: Everything
ブレーザー: Blazer (top layer)
ベスト: Vest
リボン: Ribbon
シャツ: Shirt
スカート: Skirt
ブラ: Bra
パンツ: Panties
着て: Wear
着ないで: Don't wear
脱いで: Take off
脱がないで: Don't take off
Special:
リボン付けて: Wear ribbon
リボン付けないで: Remove ribbon (naked-er is okay)
スカート・パンツ履いて: Wear skirt/panties
スカート・パンツ履かないで: Remove skirt/panties
ブラ外し: Remove bra (?)
ブラ外さないで: Wear bra (?)
※I don't remember if this is actually in the game, and I'm not about to figure that out.
Extra special:
ダブルピースして: Double peace! (You won't be asked not to.)
Just remember to go back to what you were doing before the double peace.