A great evil is sweeping over the realm; an evil that the young swordsman Roan and his life-long companion, the acolyte Yufa, must face head on! For these two travel toward their destiny, from the highest towers to the depths of the underworld, through forest and desert alike. With an ever-growing cast of fellow heroes, fate will grasp these travelers by their very souls and propel the band of skilled adventurers towards a noble end. Or ignoble, if they don't watch their step! Monsters are afoot and the way rife with danger and magic, the path forward may be unclear... But where will is strong, there is a way! Lessons wait in the depths of darkness, and good must prevail. The journey starts now! (Source: FUNimation Entertainment)

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.

In the technologically and magically advanced Wahrheit Empire, rumors of a returning catastrophe known only as the "light" causes a disturbance amongst the people. Meanwhile, in the capital of the Empire, transporter Innumael Grauer prepares his daily deliveries, struggling to make ends meet for himself and his sister. Leocadio Wöhler, a newly recruited soldier, assists Innumael whilst commuting to work—unknowingly loading a mysterious package containing contraband artillery belonging to a criminal organization.

Innumael is accused of smuggling the package, facing possible execution due to the Empire's strict oversight of weapons in response to the rising disorder. However, unbeknownst to him, the very syndicate that placed him in this unfortunate predicament may save him from this fate, at least temporarily. Elsewhere, Leocadio is assigned his first mission—to apprehend the criminal group known as "Headkeeper," suspected of transporting illegal weaponry.

Magatsu Wahrheit: Zuerst follows these two young men on a journey encompassing the Wahrheit Empire, triggering a chain of events that will not only change their lives but also alter the course of the Empire as they know it.

[Written by MAL Rewrite]

Akari Mamiya, a first-year student from Tokyo Butei High, idolizes the S-rank Butei Aria Holmes Kanzaki and wishes to follow in her footsteps. Despite only being an inept E-rank Butei, Akari's resolve to improve remains strong. After the idea of having an Amica contract (a senior-student mentorship program) with Aria is brought up, Akari submits a request form attempting to establish said contract. Her classmates and friends do not expect Aria to accept Akari's request, mainly because of the girl's strict selection process, but to everyone's surprise, Aria gives Akari a chance through a test, which Akari miraculously passes! However, Aria will not officially make Akari her Amica until Akari meets her standards. Training under Aria will be no easy feat, as she has to concurrently manage her relationships with her friends. Will Akari have what it takes to walk down the same path as her idol?