Omake Gif Anime - Joshikausei - Episode 9 - Momoko Makes Shadow Shape

Momoko played with her shadow on her way from school, but she wasn't sure she was making anything recognizable.

This is a flashback to when Mayumi first transferred to Momoko's school and saw her making rude gestures, or so she thought, in class. We finally got an explanation for why Mayumi wears a different uniform, and that she's not some younger girl that tags along with Momoko and Shibumi.

Mayumi ran into Momoko making shapes with her shadow and realized that's what she was trying to do during lunch instead of flipping people off. And that's how these two became such close friends.