Chapter 173

Short Summary
Once the dust cleared up, the class was horrified to see a weakened Korosensei covered in ash and smoke. Yanagisawa commanded the Reaper to attack the students once more, forcing Korosensei to take every hit. Having enough, Karasuma held Yanagisawa at gunpoint, but ended up getting knocked away as a response. Before Yanagisawa (and Nagisa, thinking to himself) could declare the class as Korosensei's greatest weakness, the latter proclaimed otherwise. Korosensei acknowledged that they had put their lives at risk to save him and their affection for him was the best gift he could ever receive before declaring they were not a weakness, they were his students and it was his job to protect them. In response, Yanagisawa announced that both he and the Reaper would torture the students to death once they killed Korosensei.

To the class' and Korosensei's surprise, the Reaper dodged a knife attack from Kayano, who told Korosensei that she would distract the Reaper to let him recover. She explained that she regretted how she forced the class to learn the truth and asked to redeem herself by protecting him, to which Korosensei responded that she made the right decision and that the class was able to learn what was important. With a wicked smile, Yanagisawa signaled the Reaper to kill her. As Kayano lunged toward the Reaper to attack, she thought to herself that she can land the kill, adding that the ones who taught her that were Korosensei and her sister. The Reaper then landed a punch through Kayano's chest, horrifying both the class and Korosensei

Yanagisawa burst into laughter at the apparent fact that both sisters had died in front of him, and added that he would have kept Kayano as a replacement for her sister if she didn't have a hole through the middle. Completely enraged, Korosensei shook the ground as he powered up to change the color of his tentacles to black.