I never realized throughout season 1, the moon is like this for a very specific, metaphorical reason. This and many other seeds planted throughout the show will now come together for one of the best endings in all of anime.

This will be a spoiler review because if you wanted spoiler-free you should just read a season 1 review. Also the direction the plot went with is not exactly surprising, I saw it coming, you probably saw it coming as well. It is the incredible execution that really made it shine.

The crescent moon is symbolism for many things but primarily it is Korosensei's heart, a huge chunk is missing from it because of his monstrosity both physically and past deeds, with the explosion on the moon having the same source as Korosensei. However, the crescent moon is also said to be the most beautiful by many, as if the missing chunk somehow froze the moon in its most beautiful phase. The moon finally collapses after Korosensei is gone but it is said to return to its original appearance, which I believe signifies a classic storytelling technique, that is the adventure into fantasy but ultimate return to reality.

Stories are told this way because on the one side we can have exciting fantasy elements like being assassins, but on the other hand without losing relevance to the real world. It is in theory possible for the students of E class to have this kind of growth without any of these fantasy elements, maybe Yukimura-Sensei was never working part time in that lab and she simply continued to teach these kids, and it would've had the same outcome. Ultimately it was her enthusiasm to teach that made the real difference, with or without all the tentacle tech stuff.

If the first season had an emphasis on what the teachers can teach the students, this season has an emphasis on what the students can teach the teacher. Korosensei, Karasuma and Bitch-Sensei all learned something from the students and that is a great message to have. The final bad guys are defeated by "power of friendship" but it did not feel cheap or cliche at all because it was 100% earned. Korosensei also pulls a deus ex machina, rebuilding Kaede's heart and reviving her back from death, again without feeling cheap because we know he's been preparing for this since the very beginning of the story. But also, because this whole adventure as previously mentioned, can be seen as a fantasy adventure that did not necessarily happen literally, this revival is not only forgiven, it builds character for Korosensei, showing how committed he was to becoming a better person.

Bitch-sesei I felt was under developed in this season, I like how they're unafraid to make her a 100% seduction specialist, but as she said herself, this means she can be useless in an environment where everyone knows her. Even in season 1 she had very little to do including that last arc. In season 2 she really just had nothing to do, and I think there is missed opportunity for her to maybe teach something to the students that would come in useful in the final battle.

This story is lacking that highest level of foreshadowing and payoff seen in works like Attack on Titan. Things that happen toward the end don't contradict previous development and are really good in terms of the message they convey, there's just not that "how did I not see this coming?" feeling you get from AOT. For example Kayano is revealed to be Yukimura-Sensei's sister, ok that means sense, and it serves the story well in a poetic sense, but there's absolutely zero hint this was going to happen so it was impossible to predict.

I also feel like Korosensei's cheerful personality since the very beginning does not make much sense when you consider this is supposedly only days after the starting incident. It seems like he's only that way because the story wants that tone from the beginning. I think a truly masterful writer would probably choose to start the story some time after the incident, and then go back to the beginning later on when it is appropriate, to both preserve the tone, implement more hints and also make Korosensei's transition more natural.

Throughout the show I've been thinking of some special connection between assassins and teachers, and it seems like the only plausible one is you need a broad knowledge base? That's really flimsy though I'm sorry I just can't think of any except the author wanted to write a story about teachers and needed a gimmick to make it cooler. I do however, love Nagisa the lady assassin, that connection was pretty smart.

2 bonus points for attendance 1 bonus for Nagisa the lady assassin I usually do not include bonus points in the official score below, but in my mind it has 7/5 for message, I've just transferred those 2 points into the bonus category. Despite its flaws, the perfection of its ending makes up for everything else.

So after reading some interviews it turns out the "assassin" theme do have a lot of relevance, just not with teaching specifically. The point is that assassins are assassins because they can't defeat their enemy head-on, assassins have obvious weaknesses like for example Nagisa is a short weak guy. Being an assassin means avoiding your weakness, finding your strengths and maximizing those strengths to achieve your goals. Most members of society are assassins in this way, because we each specialize in something while leaving our weaknesses to be covered by others. For example you may be an amazing musician, that's like your hidden blade, that's your strength, but do you know how to grow crops and feed yourself? You probably don't, but that's fine because there's someone in the world who does, and they will cover this weakness of yours for you. Therefore teaching kids to be assassins is like teaching them to be good members of society, and that's the purpose of this "assassin" theme.

At first Korosensei seemed like this perfect being with no weakness, but his weaknesses are slowly revealed to us, with some of the biggest ones toward the end, we learn that his heart is right under his necktie which is already punctured so it can't even stop the rubber knife. There is a parallel being drawn between humanity and weakness, when Korosensei is finally revealed to be full of weakness, is when he became the most human. I'm sure this was the intended interpretation but again, it will fall short of the highest level of writing because if you think about it, this parallel also means the better you become an assassin the less you are human? But didn't we just say we wanted the students to be better assassins?

Yes I am taking the analogy too far, but a better analogy would have had more room for interpretation.