During one of their space travels in the galaxy, Boyfriend and Girlfriend happened upon a pink-haired pigtailed girl, who immediately challenged our blue-haired protagonist at a rhythm battle, so help him defeat his latest foe on three custom songs for the ages:
Defeat the space girl with music!
Whether you choose the story mode or free play mode, the way you win remains the same, and it is by reaching the end of the songs, which you can only achieve if you play all the notes following the charts.
This is done by pressing arrow keys at the same time as the identical arrow symbols above BF match one another, but know that if you miss doing it multiple times in a row, you lose and have to start again from scratch. Good luck, enjoy!