Here are my top picks for anime like Chaos Dragon: Sekiryuu Seneki. Keep in mind the list is in no particular order. Enjoy!
Owari no Seraph
One day, a mysterious virus appeared on Earth which killed every infected human over the age of 13. At the same time, vampires emerged from the world’s dark recesses and enslaved mankind. Enter Hyakuya Yuuichirou, a young boy, who along with the rest of the children from his orphanage, are treated as livestock by the vampires. Even in captivity, Yuuichirou dreams big. He dreams of killing vampires. He dreams of killing them all.
Pandora Hearts
To young Oz Vessalius, heir to the Vessalius Duke House, the perilous world called the Abyss is nothing more than a folktale used to scare misbehaving children. However, when Oz’s coming-of-age ceremony is interrupted by the malicious Baskerville Clan intent on banishing him into the depths of the Abyss, the Vessalius heir realizes that his peaceful life of luxury is at its end. Now, he must confront the world of the Abyss and its dwellers, the monstrous “Chains,” which are both not quite as fake as he once believed.
World Trigger
One day a gate to another world opened in Mikado City. This entities of the other world, called Neighbors, sent out an invasion force that overran the area surrounding the gate. Given the technological superiority of the Neighbors, the destruction of the city seemed only a matter of time. But then suddenly Border appeared in the town, an organization that researches the technology of the Neighbors to protect this side of the gate. In a short time they built a huge base and became established as the line of defense against the Neighbors. One day a student named Yūma transfers to the same middle-school class as Osamu, a teenager who belongs to Border. He has a weapon called Trigger that is only allowed to be possessed by people in Border, and claims to have come from beyond the gate.
Black Butler
In Victorian-era Europe, a young boy loses everything he once held near and dear to a vicious plot. In his moment of death, he strikes a deal with a demon: his soul, in exchange for revenge. Ciel Phantomhive is now the head of the Phantomhive corporation, handling all business affairs as well as the underground work for the Queen of England. His new partner is a demon butler, Sebastian Michaelis, whose prowess as a butler is only surpassed by his strength as a demon.
The story follows the two along with their other servants, as they work to unravel the plot behind Ciel’s parents’ murder, and the horrendous tragedies that befell Ciel in the month directly after.
Shiki
Fifteen-year-old Megumi Shimizu dreamed of a glamorous life in the big city; however, her unexpected death in the quiet village of Sotoba marks the beginning of what appears to be a ferocious epidemic that turns the hot summer into a season of blood and terror. A young doctor named Toshio Ozaki begins to doubt the nature of the disease and comes to understand that to discover the truth, he must abandon his humanity. Meanwhile, Natsuno Yuuki, an antisocial youth from the city, is haunted by the sudden death of Megumi and must realize the pain of friendship in the face of his own tragedy. Toshio and Natsuno form an unlikely pair as they work together to save Sotoba before it transforms into a ghost town of vampires.
Arslan Senki
In the prosperous kingdom of Pars lies the Royal Capital of Ecbatana, a city of splendor and wonder, ruled by the undefeated and fearsome King Andragoras. Arslan is the young and curious prince of Pars who, despite his best efforts, doesn’t seem to have what it takes to be a proper king like his father.
At the age of 14, Arslan goes to his first battle and loses everything as the blood-soaked mist of war gives way to scorching flames, bringing him to face the demise of his once glorious kingdom. However, it is Arslan’s destiny to be a ruler, and despite the trials that face him, he must now embark on a journey to reclaim his fallen kingdom.
Akame ga Kill!
Night Raid is the covert assassination branch of the Revolutionary Army, an uprising assembled to overthrow Prime Minister Honest, whose avarice and greed for power has lead him to take take advantage of the child emperor’s inexperience. Without a strong and benevolent leader, the rest of the nation is left to drown in poverty, strife, and ruin. Though the Night Raid members are all experienced killers, they understand that taking lives is far from commendable and that they will likely face retribution as they mercilessly eliminate anyone who stands in the revolution’s way
References: MyAnimeList, ANN, Wiki