Hibiki Tachibana has defeated many powerful enemies, saved countless innocent lives, and escaped from numerous desperate situations, but she is currently finding herself unable to escape from her most desperate situation yet—summer homework! Although her high school life is relatively unremarkable, her career as a member of the military organization S.O.N.G. is anything but. Using powerful, ancient armor known as Symphogear, Hibiki and her teammates work with the United Nations to deal with international disputes and disasters. During a mission briefing at headquarters, Hibiki is made aware of a mysterious organization known as the Bavarian Illuminati, who has been responsible for several major disasters in the past and currently operate in the war-torn country Val Verde. Together, Hibiki and her team infiltrate one of the Bavarian Illuminati's manufacturing plants and free hundreds of slaves. Exposed, alchemists Saint-Germain, Cagliostro, and Prelati reveal themselves as the organization's top brass, and—using alchemical powers—declare a global revolution while sacrificing thousands of lives. Faced with yet another threat to the world's survival, Hibiki and her allies must confront the Bavarian Illuminati in their most difficult and destructive battle yet. [Written by MAL Rewrite]

To find a way in rescuing Pokota's country Taforashia which was sealed by Rezo, Lina and her group are in search for the Hellmaster's jar in what the Red Priest placed his soul after death. Zelgadis is willing to do anything to get the jar for changing back into a human while Zuuma is plotting on revenge and accomplishing assignment in killing Lina Inverse. Still a big mystery for her and the others is what Xellos is aiming for in this battle. (Source: ANN)

A new island resort has been built in Tokyo bay, and it is run by one of the world's most powerful super computers. The City Hunter gang has been invited to the grand opening party, but only Miki & Kaori have gotten there. Soon, they and the rest of the party goers are taken hostage by an exiled South American dictator called General Gillium. Now it's up to Ryo and Umibozu to free the hostages, and prevent Gillium's daughter from using the super computer to launch a nuclear attack on the USA. 

(Source: ANN)

A young Taiwanese assassin codenamed "Glass Heart" committed suicide by jumping off a building, and her heart was pierced by metal fence. Miraculously, her life was saved by heart transplantation. During her recovery she began to experience strange dreams, which lead her to Japan looking for the donor of her heart, who happens to be Kaori Makimura, former partner of City Hunter Ryo Saeba. The author mentioned in the first tankoubon volume that Angel Heart only shares the same characters of City Hunter but not its continuation. The events are all parallel universe, therefore it has nothing to do with City Hunter.