Brain dump after watching Classroom of the Elite Season 4 Episode 10

I am a light novel reader for this series and this note includes a spoiler.

I watched the Classroom of the Elite, COTE, season 4, episode 9. First of all, this episode showed that Ayanokoji cannot become a weeb. That's most important thing in the episode.

Throughput this episode, it's good to see the animation of what's happening in this exam, especially it's hard to think what happens. Some history quiz or the anime quiz on the beginning is obvious, but the scene where Nanase took a rest was just on a few rocks without any water in a forest, for example. Why didn't find a place to drink water there. Also, it was great that Sudo didn't believe Nanase as he saw what she had done.

In the other scene, then Ayanokoji kissed Karuizawa. That scene doesn't show Ayanokoji's eyes at all so it's... scary what he thinks. Probably no face change, though, contrary to Karuizawa's blushed face.

What Nagumo did was something I didn't get and also forgot. He did something but... what was it in the LN?