High school student Kazuki Muto thinks he's saving a girl from a monster, but it turns out that she saves him! Kazuki is killed while fighting a homunculus, a malevolent creature that feeds on humans. The girl, Tokiko Tsumura, revives him by replacing his heart with an alchemical device called a kakugane. With this device Kazuki can create his own Buso Renkin, an alchemical weapon in the form of a huge lance, capable of destroying homunculi. With his new weapon in hand, Kazuki decides to join forces with Tokiko to eliminate the homunculi and destroy their master, the strange and eccentric Papillion Masked Creator!
S01:E02 - The True Form Homunculus
Tokiko and Kazuki visit the haunted factory where everything began. There, they find the remains of victims and a homunculus incubator. The homunculi made there lodge themselves onto humans and consume them...
S01:E03 - You've Become a Little Stronger
A homunculus embryo has lodged itself on Tokiko, and a week remains before she becomes a homunculus. Between bouts of training with his lance, Kazuki and Tokiko search for the creator of homunculus in order to obtain the antidote.
S01:E04 - Another New Life
Kazuki and Tokiko search for a student who has been absent from school for the past four days and come across a sickly third-year student who turns out to be the creator of the homunculi...
S01:E05 - To Protect Someone
Evading the homunculus Washio's attack, Kazuki and Tokiko fall back to form a plan. The two devise a series of high-speed attacks, but Washio's natural instinct and warrior experience sees through their plan.
S01:E06 - The Butterfly of Black Death
Seeking the antidote, Kazuki goes to Chono's house, where Chono's father tells him he has cut ties with his son. Kazuki heads to the warehouse behind the Chono household, the very place where his ancestor conducted his alchemy research...
S01:E07 - Whether or Not You're a Hypocrite
Captain Bravo of the Alchemist Army recruits Kazuki to be Alchemist Warrior. Anticipating underground enemy activities within Ginsei City, Tokiko transfers to Kazuki's class, and Bravo becomes the manager of the school dormitory.
S01:E08 - A Night in the Dorm
Bravo begins training Kazuki to harden him into an Alchemist Warrior. Meanwhile, Tokiko is ordered to safeguard the kakugane originally taken from Bravo's subordinate Alchemist Warrior.
S01:E09 - The Hayasaka Twins
One rainy afternoon, Kazuki comes across two third-year students, school class president Ouka Hayasaka and her younger twin brother and star player of the Kendo Club, Shusui.
S01:E10 - It Seems We're Well Matched
Both Kazuki and the Hayasaka twins cannot hide their shock at learning each other's identities as Alchemist Warrior and LXE. But the Hayasaka twins are determined to fight. Kazuki proposes to battle Shusui one on one until Ouka returns from shutting down the school security system
S01:E11 - Til Death Do Us Part
Shusui recalls his earliest memories: being abducted by a woman claiming to be his mother and the days he spent in confinement. The twins grew up never questioning the closed world they lived in.
S01:E12 - Carnival
In the forest outside of Ginsei City, Bravo, Kazuki, and Tokiko decide to infiltrate the LXE hideout and take down the LXE before they can revive the Warrior Traitor, but they find the place empty except for Moonface...
S01:E13 - Signs of Death
Bravo rages in a seemingly never-ending battle against Moonface, while Tokiko cannot help but question and fear the intense power Kazuki is displaying as he destroys the hordes of homunculi while his friends cheer him on.
S01:E14 - Who Are You?
Stopping the Warrior Traitor is the only means to save his friends. Kazuki heads to the rooftop and with full force destroys the Restoration Flask, but finds the shattered flask to be empty!
S01:E15 - An Intermediate Existence
Becoming like Victor, Kazuki is driven by his fighting instinct. Victor leaves the scene, promising to return. Kazuki tries to follow, but thanks to Tokiko's sorrowful cry, he regains his consciousness.
S01:E16 - New Strength
Kazuki and the gang are enjoying the summer, except for Tokiko, who sneaks off to meet with Gota Nakamura, the newly appointed Alchemist Warrior, who informs her of their new mission.
S01:E17 - When Dawn Comes
Thanks to the power of the black kakugane, Kazuki is revived. In order to deal with the black kakugane, Kazuki decides to go to the place where Tokiko found it. Tokiko tells Kazuki that she will not leave his side.
S01:E18 - The Escape
Kazuki, Tokiko, and Gota head toward the Newton Apple Academy for Girls, an all-girl boarding school where the black kakugane was originally located. Warrior Chief Hiwatari and his re-extermination squad are pursuing Kazuki but are stopped by Papillon.
S01:E19 - As Long as I Can Protect You
Caught in the explosion created by Hiwatari, Tokiko and Gota stray from Kazuki. Meanwhile, the search and destroy team locates Victor and launches a full-scale attack. But the ability of Victor's Buso Renkin to control gravity proves too powerful.
S01:E20 - With Strength and Feeling
Without speaking a word, Kazuki and Bravo battle to settle the score. Kazuki attacks with his lance, but even that is not enough to penetrate Bravo's Silver Skin. Bravo accepts Kazuki's growth as a warrior and reinforces his will to re-exterminate Kazuki.