"Seven Deadly Sins: Seven Scars They Left Behind" is a manga that serves as a prequel to the main "Seven Deadly Sins" series, exploring the backstories of the titular group and the events that shaped their lives before the primary narrative. The story is structured around seven key scars, each representing a pivotal moment in the lives of the Sins, delving into their pasts and the emotional and physical wounds they carry.

The narrative begins with Meliodas, the leader of the Seven Deadly Sins, whose scar is tied to his tragic relationship with Elizabeth and his internal struggle with his demonic heritage. The story reveals his fall from grace within the Demon Clan and his eventual decision to betray them, leading to his exile and the formation of the Seven Deadly Sins. Diane, the Serpent's Sin of Envy, is explored through her isolation as a giant and her longing for acceptance, culminating in her bond with King, the Grizzly's Sin of Sloth. King's own scar is rooted in his guilt over failing to protect his sister Elaine and his subsequent withdrawal from the Fairy King's responsibilities.

Ban, the Fox's Sin of Greed, is depicted grappling with his immortality and the loss of his beloved Elaine, which drives his relentless pursuit of power and his eventual imprisonment. Gowther, the Goat's Sin of Lust, is revealed to be an artificial being created to understand human emotions, with his scar tied to his creator's tragic fate and his own struggle to comprehend love and identity. Merlin, the Boar's Sin of Gluttony, is shown as a prodigious mage burdened by her immortality and her unrequited love for Meliodas, leading to her decision to seal herself away.

Escanor, the Lion's Sin of Pride, is portrayed as a man cursed with uncontrollable power tied to the sun, which isolates him from others and fuels his internal conflict between his daytime and nighttime personas. Each character's scar is a reflection of their deepest regrets, losses, and the events that forged their identities, providing a deeper understanding of their motivations and relationships within the main series.

The manga weaves these individual stories together, highlighting the interconnectedness of the Sins' pasts and the shared trauma that binds them. It also introduces key figures from their histories, such as the Demon Clan, the Goddess Clan, and the Holy Knights, who play significant roles in shaping their destinies. Through its exploration of these scars, the series offers a poignant and layered examination of the characters' struggles, sacrifices, and the resilience that defines them.