Over a century ago, mankind was devoured by giant beings of unknown intelligence and origin known as Titans – creatures that eat humans alive indiscriminately and for no apparent reason. The remaining population has managed to survive the last hundred years only by building a multi-walled city capable of keeping the Titans at bay, training military recruits to patrol the perimeter and gather intelligence about their mysterious foe. Eren and Mikasa have lived a relatively peaceful life behind the city's walls, but when a massive Titan appears, smashing the outer barrier and unleashing a wave of terror, their lives are brutally changed forever...
Much to the annoyance of Kei, he and his childhood friend Katou have died, having been torn apart by a train. But rather than finding themselves at the gates of heaven, the duo materialize in a room full of strangers and a giant black sphere known as GANTZ. As if dying once wasn’t bad enough, the occupants of the room are then forced to embark on dangerous missions to kill strange aliens; missions that very few return from. Now, Kei, Katou, and a well-endowed friend must fight for their freedom with an arsenal of guns, high powered suits, and a very low chance of survival.
This is similar in that they are both tragedies. They have giants involved...although not alien monsters, they are basically the same where it is humans vs. giants. It is a tragedy and twisted in its own way.
In both of these animes people are thrown in to desperate life and death struggle against vastly superior enemy. Gory death scenes of people dying in vain.
Both of these shows depict people fighting against inhuman monsters/aliens that are much stronger than them. Both contain the thrill that any character could be killed, not just minor ones.
22-year-old Ryouta is an unemployed good-for-nothing who spends his days living at home and playing Btooom, a wildly popular online game that's sold over three million copies worldwide. Alongside other teammates, Ryouta battles it out with others using powerful bombs and sonar that can reveal hidden enemies, and his dedication has earned him the title of Japan's top player. But soon, Ryouta's pastime becomes a terrifying reality, as he and many others are dropped onto a tropical island and forced to play Btooom – but this time for real. Now, he and the rest must fight to the death by whatever means necessary, as the only way to win this deadly game is by killing seven of the other players.
Both anime are really bloody and really focus on the phycologial parts of people's actions. Filled with action and strategizing that is close to the feeling you get when you watch code geass.
Both of these shows focus on the despiration and need for survival both portray in their situations. Where one is about being stranded on a island forced to kill one another, the other focuses on the despiration on not wanting to be eaten by the Titans. The survival aspects are key with both.
An akuma is a soul which has been brought back to life through sadness and despair with the powers of Millenium Earl. Their mission is to terrorize the earth and all who dwell within it. The Black Order is a group of Exorcists that have sworn to cleanse the souls of the akuma, and collect the substance known as "innocence". This powerful substance can be used as an anti-akuma weapon, and ultimately can help destroy the evil Millenium Earl. Allen Walker is a young Exorcist who has the ability to tell who is human and who is an akuma with the help of his cursed eye. Together with the Black Order, Allen must find all 109 pieces of innocence to protect the world and defeat Earl.
Both of these series gives us the sense that they are fighting a losing battle. In D. Gray-Man, there is only a small, limited amount of exorcists but an increasing amount of akuma, while in Attack on Titan, humanity's population and land keep decreasing and they keep advancing. We are kept on edge all the time, and small victories seem thwarted by larger losses.
Both of them have a similar theme of young men istruggling with their pasts and the powers they control, joining military organisiations, and fighting for mankind against a common enemy.
For Kouta and Yuka, finding the bloody naked young girl on the beach would change their lives forever, for better or for worse. Unable to speak or function as a normal human being, she is named Nyu by the duo, and taken into their home in an effort to save her. But what neither teenager knows is that this innocent young girl is actually a killing machine -- an experiment gone terribly wrong -- and it is only a matter of time before the murderer in her awakens again...
even though the stories in both animes are totally different, there's this same atmosphere in both, they both contain a lot of gore, blood, flying limbs, etc. and even though the stories are different, they are both really exciting
the characters aren't alike at all either, but that just makes it better, they're not alike, but they do share some things, so that if you like one, you'll also like the other one
Like above, the gore and brutality bring these two together, but also both draw the viewer in to the world. Both are tragic, and you'll probably be crying and flailing in either one. I wouldn't watch the two back to back, that's for sure.
Once upon a time, two brothers passed the happy days of their childhood by studying alchemy, which is governed by the equal transfer principle: an eye for an eye -- you can't get more than you give. But these brothers tried to defy that law, and a horrific accident resulted. Now, the older brother, Edward, is called the Full Metal Alchemist because of his metal limbs, and the younger, Alphonse, is a soul without a body, trapped within the confines of an automaton. Together they search for the power to restore themselves, to find the lives they lost so long ago...
Both of these series feature an angry young soldier motivated by the death of his mother and dealing with the horrors of war. Both series are also set in a European-ish setting that feels historical but doesn't quite fit into real-world history, with strange-but-cool technology. Also, both series feature a mysterious father figure with a secret that might solve some of the series mysteries.
It's not a completely perfect rec--FMA has plenty of comedy in it, while Attack on Titan takes itself VEEEERY seriously (for the most part), but I definitely think they have a similar appeal.
If you liked Attack on Titan, but would like something similar, but maybe a little more light-hearted - check out Full Metal Alchemist.
Both anime share a grim and dark core in a world where evil is a very real and present ever-constant threat. Both heroes have been transformed by tragedy, and are exploring ways to avoid being consumed by the world around them, and are also struggling in a greater fight to save the world from the evil horrors they are combating.
But FMA adds comedic touches and elements of humor not present in AoT and ends up feeling a bit lighter in tone. If you liked Attack on Titan and are ready for more, but not yet ready to cope with too much more bleakness and despair, do yourself a favor and watch Full Metal Alchemist.