During its first season, Ansatsu Kyoushitsu (Assassination Classroom) was considered one of the best. It ranked 4th in the TOP best-selling mangas of 2015.
The first live-action film premiered in March 2015 and the second will premiere in spring 2016. The manga ended in March and had 4 spin-off chapters about Koro-sensei's vacation.
I expected the same success in the second season; I wanted to see the students' development, new dramas, their relationships with teachers, and the prejudice of the rest of the school. That wasn't quite what happened in the anime, and my disappointment came in the first episode when it wasn't shown that Koutaro Takebayashi left Class E and went to the main building.
The way this happened, how it was exploited by the principal, and Class E's reaction were important because it deeply showed how they want the class to be seen by the other students to reinforce the principal's idealism about how education should be taught.
Takebayashi was quite inexpressive, and after this incident, he gained a fundamental role in the following events. In the anime, this was not shown, and nothing was explained, not even in a narration using Nagisa.
Everything was happening too quickly, missing small details that set the tone for both the humor and the action. Losing some context, the anime has been a bit dull and is losing its position on best-of lists. Perhaps they want to move on to the arc where the mysteries are revealed and end the anime this season exploring the most tense and decisive part.
Even though the anime didn't reach its full potential in the first part, starting with episode 15, the series entered a new arc, with a new opening. This arc will conclude the anime. The shift in mood was felt, and the revelations made it clear how serious the subject matter is and made us think about the future of Koro-sensei and Earth.
Taken from the blog: Kimiko no Nikki