This chapter opens with a flashback to the events of the previous chapter. It's the first time we've seen a flashback in this chapter, so we're not sure what's going on. It turns out that the flashback is about a girl named Setuna who was a teacher at the school where Setuna is now a student. She's a friend of Setuna's from middle school, and she's been trying to save him from drowning in the river. She tried to help him when he was in his first year at school, but he didn't want to do it, so she moved to another school. Now that he's in high school, he thinks it's safe to say that he and Setuna aren't really friends anymore. He tells us that they're going to have to ask Setuna to tell them what happened. He also tells us how sad she was when they were in middle school. He's not sure if it was because she was depressed, or if she was just trying to protect him. He doesn't know. He says he'll ask her to tell him what happened, and then they'll have to figure out who their enemy is. Everyone's having a good time at the party, except for Setuna, who's worried that he might get hurt. He wants to know what the enemy is, and he decides to do something about it. He decides to use Onmyodo and shikigami to help the enemy.