Episode 45

Final Boss Time is the twenty-third episode of Season 2 and the forty-fifth episode of the Assassination Classroom anime. It premiered in Japan on June 16, 2016.

Summary
Korosensei faces his former apprentice and Yanagisawa in a life-or-death battle. When Yanagisawa switches his focus on the students, Kayano sacrifices herself to buy Korosensei time to recover, leading to one final clash.

Plot
After struggling against both Yanagisawa and The Reaper, Korosensei takes further damage when Yanagisawa directs The Reaper to attack the students. Yanagisawa claims the students to be hindrances, but Korosensei defends his students, saying that they are his greatest gift as a teacher. Kaede attacks the Reaper, but is fatally injured in the process, seemingly sending Korosensei into a rage. However, his true expression turns out to be a mix of all of his emotions, giving him the power to kill both Yanasigawa and The Reaper, who had wanted to be acknowledged by his teacher all along. Afterwards, Korosensei, having managed to keep Kaede's blood safe during the battle, uses his skills to heal her injury and bring her back to life.

Anime and Manga differences

 * When preparing his energy beam, Korosensei's face does not change into various expressions.
 * When Korosensei asks Nakamura to get the cakes, the damage in the anime was less than in the manga itself as the cake was not entirely ruined by the soil. This includes during surgery when Korosensei eats with a fork in the anime, while in the manga Nakamura feeds him.

Trivia

 * As the Class 3-E students while wearing military uniforms were saying happy birthday to Korosensei, he's not blowing the candles on his cake.