Tried my first run using the default skills and without reading anything in the settings menu. It was jarring just being dropped into the game like that without any instruction, it took me a second of scrambling to figure out how to move, shoot, and switch character. I reached the first boss but died, I didn't know how to aim up with the girl for most of the battle so I spent a lot of time doing nothing after the brother died.
Took a look at the controls before starting my next run, this time it went much better. Killed the first boss with relative ease, but I died very quickly by the ice girl's initial burst. I kept trying until I experienced a crash during the phase where the boss drops the projectile cubes on you: I was under her using the sister, then I used a bomb (white square), which crashed the game. I tried this again and the game crashed again under the same conditions. I went in for a third time, not using the girl this time, and it randomly crashed again. Sucks.
Closing thoughts: the dialogue between the characters is cute, I could get a grasp on what their personalities are like with just a few lines of dialogue. The art is amateur at best but is still very charming, it might even work to your favor considering ZUN. I don't see why I would ever want to use the sister over the brother, considering I have to actually aim with her. I can only assume she does more damage? Anyway, this is a neat little game that I sucked pretty hard at, I can see bullet hell enjoyers liking it.