Jotei no Shouzou? Special 10.5 Seikon no Qwaser : Season 1 Episode 25

One day, honor-student Shiizaki Lulu observes Katya and Hana together in the science lab preparation room. She is discovered and caught. Katya draws close to her but suddenly stops. Shortly after, Lulu accompanies her mother to a suspicious ritual being performed by mysterious cult.