God has abandoned the world. As a result, life cannot end nor can new life be born, and the "dead" walk restlessly among the living. Granting one last miracle before turning away forever, God created "gravekeepers," mystical beings capable of putting the dead to rest through a proper burial. Ai, a cheerful but naïve young girl, serves as her village's gravekeeper in place of her late mother. One day, a man known as Hampnie Hambart, who is supposedly Ai's father, arrives and kills all the people in her village. Having lost her village and with no plans for the future, Ai decides to accompany the mysterious man on his journey. As she travels the land, the young gravekeeper strives to fulfill her duties, granting peace to the dead and assisting the living, while at the same time learning more about the world that God left in this tragic state. [Written by MAL Rewrite]

In the latter half of 21st century, humans leave the Earth and begin to live in space. In order to adapt to the environment in space and deal with the hostile aliens in Jupiter, genetically engineered children called "Princes" are artificially raised and trained to be pilots of armed robots "AHSMB (Advanced High Standard Multipurpose Battle Device). This is a story about one of the teenage "Princes," Hitachi O Izuru, who studies in an academic city Grandzehle. (Source: MAL News)

The story begins when high school student Kazuki Muto is killed one night saving a mysterious girl from a monster, only to wake up in his school dorm, believing it to have been a dream; however, he soon finds out that dream wasn't a dream at all when a giant serpentine monster attacks him and his sister. Tokiko Tsumura, the girl he saved, explains that the monster is a homunculus. Kazuki had been attacked and killed by it when he was rescuing her; however, she, feeling responsible for him, revived him by placing a Kakugane medallion in his chest, serving as a replacement heart. The Kakugane, as Tokiko explains, is an alchemical device that, when activated, takes a certain form based on the Kakugane's user, forming a unique Buso Renkin. The Buso Renkin is the only thing that can destroy a homunculus monster. Using this, Kazuki creates his own Buso Renkin (the "Sunlight Heart," a huge lance). Along with Tokiko and her own Buso Renkin (the "Valkyrie Skirt," an execution scythe), Kazuki joins the fight against the homunculi and their master.

Under Nariyuki Yuiga's devoted tutelage, his classmates Rizu Ogata, Fumino Furuhashi, and Uruka Takemoto are finally pulling average test scores on their worst subjects. But time is ticking, and there is still a long way to go before the three geniuses of Ichinose Academy are ready for their upcoming university exams. Meanwhile, the girls still struggle to balance the pursuit of their dreams with their growing affections for their unsuspecting tutor. Joining them are Mafuyu Kirisu, a teacher with strong views about education and talent because of her past as a rising figure skater, and Asumi Kominami, a graduate from their school aiming to attend a national medical university. With these two additions, the group of six is livelier than ever before. Completely caught up in hilarious antics with his new friends, Yuiga finds that his last year of high school now includes a lot more than just going to class and studying. [Written by MAL Rewrite]