They get tied together

While in the darkness, Chihiro felt his body get pushed against something he couldn't see. It felt soft, warm, wet and was taller them him.

"Hey." Aoi called out. It then dawned on Chihiro, based on how close Aoi's voice was to Chihiro, he was pushed against her.

The next thing Chihiro felt was a robe going around his body, tieing him to Aoi and forcing the two as close to each other as they could be. They were stuck together.

The lights then turned on, blinding the bound pair for a short time. Eventually, their eyes adjusted and they were able to see two of their classmates before, Sayaka and Junko.

"Hey hi, how you doing?" Junko asked in an erratic manner, Sayaka standing next to her, not understanding her accomplice's way of speaking.

"Why are you doing this? You still aren't mad about that contest, right?" Aoi asked, wanting to know why her friends had turned on her.

Chihiro was too stunned to talk, not just because of what Sayaka and Junko could do to them but also by the fact that, thanks to the lights being on, Chihiro was able to see that due to the height difference between him and Aoi, Chihiro's face was right next to Aoi's breasts, her swimsuit being the only thing separating the two.

"Don't worry about 'why', worry about what happens next." Sayaka said with a sweet smile plastered on her face.