As my last rewatch was quite a long time back, it was actually a good idea to do one now as I got to see for myself once again how underrated Kekkai Sensen and it's way actually are. Last night I wrote to someone else a huge wall of text, consisting of what Kekkai Sensen is about and how well it's structured, while scaring people away with it's episodic look. This review is honestly a huge mess as it’s freely written, has no real structure and also specifically looks into certain things, but still I decided to share my view here. Here we go:

My last watch was quite long back and now that I'm here again, Kekkai Sensen is more heavily underrated than I always thought
Like, here it doesn't even matter whether you look at the Opening, Anime itself or Ending because all just adds together to it's actually outstanding

Opening

Looking at the Opening, let’s have a small insight into how it conveys us change, day to day life and the fun you can have with the people you met.
Starting off we see Hellsalem’s Lot or former New York in the morning, the sunrise indicating the beginning of a new day and chapter in the life of everyone, while also having it turn upside down, alluding the change the city and it’s citizens went through as change will always remain part of our life.
Following with a shot of hundreds and thousands of pictures containing the different locations, people and events that took place in Hellsalem’s Lot, forming the barrier that holds New York and the Otherworld together, striking us again with the symbolism of pictures and „capturing the moment“ in Kekkai Sensen as it’s these that make everyday life so special, especially in this chaotic city.
Continuing we see scenes with Leonardo walking in the mids of masses of people in the city, together with some color changes that don’t seem out of the ordinary at first, but it’s these color changes to a black & white tone that allow us to see the world in the same light as Leo does. He genuinely thinks of himself as an ordinary person, as a part of the mass while being able to see the outstanding characters, personalities around him with a glowing color, fitting their souls. We see Klaus von Reinherz in a red highlight in the middle of people colored in black & white, symbolizing his courageous character that is willing to sacrifice himself and continue to fight for the safety of his friends and the citizens while the King of Despair/Blue is highlighted in a blue color, which could indicate the freedom he has as an immortal being, but also his sensitivity and aim towards his goal of finally getting past life. Leo enables us to see the outstanding characters in these masses, being able to see the people he considers as extraordinary or special, allowing us to enter the exciting world that comes with them.
A nice additional touch are the pictures of Leo getting up in the morning and having fun with his friends, eating burgers, pulling funny faces which all simply indicates his daily life.
Additionally we also see for a brief moment the days in the city pass accelerated, probably telling us that life will continue no matter what happens yesterday, while the scene also contains three crucial characters for the happenings in Kekkai Sensen- one character being Michella with the prior mentioned red petals falling from the sky, transitioning to Leonardo opening his eyes which once again reminds us of her sacrifice for his ability.
Coming to the key visual of the Opening, we see the huge chaos that from there on is part of his life. We see the characters he met and new friends he made, all of them showing off their abilities as each of his friends is extraordinary on their own, the screen keeps flashing up due to everything that happens and also in the future will keep happening. This is the world Leo was looking for, one extraordinary world which he was allowed to enter as an observer thanks to his eyes.
Reaching slowly the end, we lastly see an introduction of the 13 Vampire Kings, Blue and of course the stage with all the friends he made, his stage being the only one that has yet to start to glow the way the others do.

Leo

The whole show wouldn't be possible without Leo and with that without us, as Leo has been introduced from the beginning on into the position of the watcher, the observer that made everything just possible. He became the power to see as higher beings do, making us to that higher being as the viewer. That's also why the camera of Leo is so important as plot device actually, we capture the moments and events and from overarching view and have them remain in the total, whether it's important or not. Pictures are there in every episode to remind us of Us and Leo to be the observer.

In ep 11 though they went even beyond with that which is plainly amazing, as it was White's backstory from when she was still a child. She has no powers while Black and their parents do, doesn't see a meaning in her as there is nothing she can do for this world while her parents used their powers to help other people. So what she does it to take pictures of others, but never from herself as she sees these photos as something she actually accomplished while she was still alive- later her camera was thrown by others from a bridge into the river, while Black tries to catch it and has a small incident because of that, having her telling him that the camera is actually just a placebo in the end as it still means that the photos are just functioning as placeholders for the moments, but can't revive a dead person. Something else that's important here is that it also shows the difference in Black and White as he has the potential to become the same as his parents and help the world while she can't and doesn't really know what to do in life, the photos don't have any real worth compared to the others in her family. That's her placebo, she tried to have something she can do to leave it behind in this world while Black can't. BUT very amazing is also when afterwards during the night Black took a photo of her that made her cry, that was the recognition and proof that she was alive and valued by others, which is a huge impact point. So even if she does nothing, she is still important to her brother. THAT'S WHERE WE GET BACK TO LEO'S CAM!! She helped the king of despair/Black to get to Leo's eyes because she wants Black to get his own life back again, but when then when the monkey gave her Leo's cam, she started to look through the photos on it and realized her mistake. The first photo in the gallery is Leo's sister, the person he values most and afterwards he already put White. The third picture we see is one from Leo that she took, being that reminder for how important he actually is to her! The meaning behind the camera and pictures being that whatever we see on them, it was important enough for someone to capture the moment. To "immortalize" it. This is also where I love the contrast to White's brother Black or rather the King of Despair, as the dead and moments of the past are hold on picture forever while he himself can't die. He doesn't get the luxus to die and lives on forever, which is why he planned to destroy the world and eventually die with that. Leaving a proof that he was alive once too. That's why even the king has taken photos and recorded video tapes of himself because he thought he can finally pass on, he wanted to leave them as the proof that he lived and that even though he is well-aware of his immortality. The contrast of White & Black and the meaning of the Observer role and the camera + photos in this show is plainly amazing to me, I love it too much.

Ending

Getting back to the first paragraph of this main body, it also doesn't matter what exactly is going on at given moment or time, as everything that can happen is part of the telling and how life goes in Hellsalem's Lot. It's just a huge stage performance that allows characters to be changed, swapped and it doesn't even matter whether the char is considered good or evil as the play will still go on into it's next act. Anyone can be in the focus of what's to see.

That's something that makes the Ending even better than it already was before, as it shows us that stage with the characters acting freely, dumb, doing shenanigans, see short moments of the different characters interacting but even there we remain with the role of an observer as the lights on stage don't differenciate between good and evil chars, but put their spotlight on what's seen. Whoever and whatever is on the stage right now. It doesn't matter what's going on in the world, whether it's going down or the city is getting completely destroyed, the show just allows us to invest into it's characters and they being it's actors. Further, the Ending symbolizes a lot with the colors white, black and red (basically blood). For uni I once looked up the meaning of colors and how colors can and are used in stories to convey a symbolic meaning, which the ED does too with red roses representing the sacrifice of characters as we can see in the scene with Leo and his sister, having red petals falling during that tragic moment of her losing the ability to see. Next we see a white rose which often symbolizes loyality or undying love, that's dragged by White with her feet and starts to blood, as she is part of the barrier that holds the city together and which she remains able to due to her love for her family. That scene even foreshadowed in the ED already that she is gonna sacrifice herself to save her brother and Leo. In the next shot we already see Black and the king of Despair (which is essentially blue) surrounded by black and blue petals, which also contrasts with the other two colours and fitting their names + designs for the show. Further Black holds bouquet of white roses to symbolize his love for his sister while the king only does hold one, in both cases showing the importance of White to both as Black feels complete with her while the king needs her for his plan to destroy everything. But at the end I really love the shot from the fist holding a white rose with blood that's supposed to mean the victory at the end of s1, that's been achieved by sacrifice as White sacrificed herself and the red petals representing the sacrifice Leo's sister contributed at the beginning. Without both sacrifices Leo never could've won, holding the white petal that's streamed with blood

More

I love how Kekkai Sensen is theoretically episodic as many episodes just feature a one ep arc and them being loose in their telling from all the others, but still managed to have an overarching plot that results in the climax of season 1 and with that in an outstanding end.
It knew how to use itself, how to use and build a limitless world that allows any Shenanigans you can think of. How to use the characters and give them here and there spotlight. How to entertain you with absurdity and still trying to teach you values with the observer, Leo, who had nothing to do at the beginning and didn't know how to continue, up to the point that he learned how to look ahead and keep moving forward, trying to take steps towards the light. With that he also finally managed to write the letter to his sister, telling her about the world and light he was able to see thanks to her.
The concept of Kekkai Sensen, it's potential and the involvement of an observer and thus us is likely one of the most amazing things I've seen in AniManga, enabling it to be this much fun. Leo, giving us the ability to experience the events from the perspective of someone that was given the power to see everything, making us the higher being that records them, is something I love the most about it.

This may be the end of the review, but honestly, I still didn't write enough. There is so much yet to mention, so many characters I still have to look into, how the show has some of the best OSTs I've ever heard and other things. Honestly, it's a pity that I'm at the end, but at the same time I think that it's best to experience the characters, music and action on your own, to see why they make Kekkai Sensen this amazing. As poorly written as this Review may be, I still hope I managed to tell you about what Kekkai Sensen is