If you're looking for anime similar to Ifrit: Danzai no Enjin, you might like these titles.
Aya, Omi, Ken and Yoji are four seemingly normal high school boys, who make up an elite assassin group known only as Weiss. The hits involve taking out corporate businessmen and corrupt politicians; however, trouble arises during a routine job, when Weiss clashes with a rival gang of assassins, Schwarz. With Schwarz in the way, they will reach the limits of their elite skills while trying to defeat their ultimate target: the Takatori family...
After Jean and Rico finish a mission, Jean and José head off for a short break with Rico and Henrietta. They visit their old home, and Jean reflects on old memories of their younger sister, Enrica, who died in a terrorist attack.
After Akira and his sister Kaori are falsely assumed dead in the accident that killed their parents, they are now seeking revenge on the organization responsible for the deaths, even if it means breaking the law. Weiss Kreuz is asked to stop this duo from committing their illegal activities, but Aya and Yoji are the only two who accept the mission. While carrying out their plans, the entire Weiss team finds themselves in the lair of death and deceit. Will the organization's ruthless plan mean the fall of Weiss?
There is trouble afoot at Koua Academy, home of an intellectually elite selection of students and teachers. The mysterious S-Class is not only the best of the best, but the superior force behind the actions and administration of the entire school. However, a recent chain of suicides has raised the attention of more than just the media. Weiss must band together for one last mission: to hunt down the evil mastermind responsible for the suicides and secret experiments at Koua Academy: Epitaph.
The story begins after 70% of the moon was suddenly vaporized in an explosion. The super lifeform responsible for this catastrophe is a strange tentacled creature that can slink around at supersonic Mach 20 speeds. It has a 10 billion yen (US$100 million) price on its head, but for some reason, this creature ends up teaching a middle school class at the beginning of the school year. The students have until graduation to assassinate the teacher, or it will destroy Earth as well.