Intro:
(Please forgive me, this is my first MAL review.)
~Slight Spoilers Follow~
Owari no Seraph (English: Seraph of the End) may at first seem like your average action manga series with a super angry protagonist, but don't let the exterior fool you. It has more depth into it than you think.

Story: 9/10
Seraph of the End has a story that starts of with a unique setting. A mysterious virus that kills anyone over 13. Vampires who have been in hiding seize that chance to come to the surface and try to gain power amidst the destruction. Yuu and Mika, two central characters in the story, are captured by vampires (along with the rest of the children from their orphanage) for their blood. Skip to six years later.
After losing his family four years ago, Yuu seeks vengeance for his dead 'family,' especially Mika. This part of Yuu eventually fades away after learning that Mika is alive. The story starts to twist and turn and spin out of control as Yuu tries to figure out more about Mika and Mika tries to figure out more about Yuu.
The term 'seraph of the end' in terms of the story comes from Yuu's experiences, as you will learn early in the story. Yuu had been experimented on by the infamous Hyakuya orphanage for extremely mischievous reasons. He had been given a so-called "seraph gene" that makes him go berserk. The plot becomes thicker when you realize more of the Hiragis' (the family that helped save some of the humans in Japan and started to Vampire Extermination Unit) motives, Guren's thinking, and the vampires' side of the story.
Mika, on the other hand, had grown up with the vampires with the hope that Yuu was alive. But he slowly starts to resent both humans and vampires—humans due to the experiments and misuse of otherworldly beings for their own selfish purposes, and vampires for the life that they ripped from both him and Yuu.
Both boys hold a close bond, and they both search for answers in each other and with each other, unraveling many secrets.
The individual arcs in the story reveal several different plot points that hint at different motives between each action. As the story progresses, you start to question which side is good and which side is bad. The lines blur and you wonder who is who. Sometimes it's shocking, and the shock gets you, but in a good way.

Art: 8.5/10
The art in the manga series is wonderful, but far from perfect. The close-ups and shading is perfect, but some shots look iffy. The art style is great for this kind of story. It helps you fall in love with the characters and the setting since everything is so nicely illustrated. But there are still those little things, here and there, that are noticeable. These things kinda bring down the quality since it might confuse the reader. But the art slowly improves. It's not god-awful, but it's pleasing.

Character: 8/10
When the reader first find Yuu in the present setting, he's bitter and tries to distance himself from others so that he tries not to make close connections and bonds with others, in fear that he might be hurt the same way he was hurt when he 'lost' Mika. But we slowly see Yuu mature from a 'kill all the vampires' and 'no friends, I hate you all' person to a more refined individual, slowly gaining new perspective on the world. His resentment of vampires holds, even though he finds his 'brother' turned into a vampire. He really grows on you, but he still holds some of those cliche character tropes of a protagonist that initially wanted me to turn away: I want to kill all ______, always angry, and I have a special power because main character. The second of the three eventually fades into easily teased. The last of the three is a (somewhat) central part of the plot, unlike in Shingeki no Kyojin where it's more like an accessory.
Mika's development is surprising—he goes from a full-of-sunshine, cheery boy to a loathsome, brooding vampire. He is essentially teen angst. But that initial impression wears off when you realize the reason behind his sulking. He desperately wants to protect Yuu. He has a complex over Yuu and you see the struggles he has. He abstained from human blood, making him cry out in pain and occasionally lose control of himself for Yuu's sake, in hopes that he will never become a 'disgusting monster.' Mika's personality is actually slightly relatable, making him a favorite.
Shinoa Hiragi is a unique girl. Her character is extremely interesting, with her background and where she stands. She appears to know so much, but she is clueless when it comes to her own sister. She is loyal to Guren Ichinose, another important character, making her seemed mixed and confusing. Shinoa turns out to be a lovable character as a funny squad leader with plans of her own.
Mitsuba, I feel, is used mostly for comic relief. You don't see much about her, anything that might stick to you, anyway.
I don't have much to say about Kimizuki or Yoichi.

Enjoyment: 10/10
I clearly enjoy Seraph of the End. It's still a young series, and so many avenues and plot lines could be explored and I eagerly wait for the next chapter. The plot is so interesting and I just get so absorbed in the story.

Overall: 9.1/10
Overall, Seraph of the End is a series that many should try. The anime does not do it justice at all. If you liked Shingeki no Kyojin or like Hellsing, Seraph of the End is the thing for you. While there are things that could be worked out here and there, I think it's extremely great. I tried it and liked it, and you might too.