In both the rescue of Kanzaki and getting revenge for Maehara it is more about what the individual does for themselves. As Kanzaki finds out who she truly is and Maehara not fall into the cycle of looking down on those below him. Even more so is the teamwork of Koro-sensei with his students that is really cool to see.
It shouldn’t be a surprise that more assassins get involved to assassinate Koro-sensei. Though once again we get to see how Koro-sensei uses that to enhance the school environment. With Ritsu we see him not being prejudiced against her since she is a machine powered by AI. The fact he was able to guide her to make her own choice is very much what Koro-sensei wants to give to his students.,
Though the volume ends with Koro-sensei standing up for Irina against the man who recommended her. I guess this can illustrate that Koro-sensei isn’t just partial to just his students, as the students grow thanks to the whole faculty, not just one teacher. Curious how he aims to prove Irina’s worth given the fact her job is to assassinate Koro-sensei.