As the students are undecided about whether to save or kill Koro-sensei, they partake in a game to decide it. Very fitting for Koro-sensei to want the students to decide it and to make sure the classroom stays united.
We see the various skills of the students and their skills. Though the big focus is on Karma and Nagisa. We have seen Nagisa develop into quite the frightening assassin when, in fact, given first impressions, one would think that would be Karma. Karma has turned out to be quite the leader when he is focused.
How Nagisa was able to beat Karma was impressive because he had to beat Karma under his rules. Probably the biggest assassin skill Nagisa showed was his ability to adapt because he did an incredible job here.
The one avenue to save Koro-sensei is to obtain the research from the US team. Quite the reckless plan, but Koro-sensei gets the rocket to launch with Nagisa and Karma. Curious how their teamwork will shine after their matchup in this volume.