I was split between 'just hypnosis' and 'some level of bodyswapping involved' since 34 and 34.5 made it clear that the Airi we saw during the chapter was always the Airi we're familiar with. Given that Airi is a certified sleepy girl and 34 already kind of indicated she was super reactive to hypnosis I'm a little annoyed at myself for not figuring out the solution earlier.
Nagi never actually breaks the hypnosis, despite the numerous warnings in both chapters? She tries to fix it by going along with what Airi thinks, which in practice takes the form of leading her through the scenario and adding more and more suggestions until Airi's mind turns into slush. That's pretty amazing for us (page 84 was beautiful...), but it's terrible for Airi.
But that's how Nagi does things, right? She accepts whatever Airi thinks because when put in a corner (see chapter 16) she wants to be accepted completely, including her codependency and toxicity, and really doesn't want to be denied at all. Nagi can't quite admit to her role in starting Airi's spiral by ending it as she begun it; maybe that parallels how she also can't quite admit to her role in making Airi the brilliant outgoing person she loves today? Might be reaching, though