Mina tells everyone to come to the common room while izuku was asleep. She tells everyone about the prank she has in mind and winner gets money from momo, ochaco hesitates at first but agrees because of the money. Tenya thought it's a bad idea but got convinced later.. todoroki only joined because of the soba. And the others agreed eventually. So it started. The entire class ignoring izuku.. bakugo of course agreed. And aizawa their teacher doesn't know about this.