From Divine Sanctuary:
Yuuki's first boyfriend is Tetsu, the pitcher of the baseball club, but... she's in big trouble because she has too many rivals in love!? After 4 months of dating, she is constantly harassed to breakup with Tetsu by his fans. Her friend Nacchi says it's because she lacks feminine pheromones!! When Yuuki asks Nacchi how to acquire feminine pheromones, Nacchi tells her that after she "does it" with Tetsu they will begin to pour out of her... but after hearing that, the only thing pouring out of Yuuki are nosebleeds from all her perverse thoughts!!
NOTE: This is chapter 4 of Body Talk - Junai Yuugi