"Spy×Family" is set in a fictional world resembling Cold War-era Europe, where tensions between the nations of Westalis and Ostania are high. The story centers on Twilight, a highly skilled spy from Westalis tasked with a critical mission: to prevent war by infiltrating the elite circles of Ostania. To achieve this, he must get close to Donovan Desmond, a powerful political figure who rarely appears in public. Twilight’s plan involves creating a fake family to enroll a child in Eden Academy, an exclusive school attended by Desmond’s son. This setup will allow him to gather intelligence and complete his mission.

Twilight adopts the alias Loid Forger and begins assembling his makeshift family. He first adopts Anya, a young girl with telepathic abilities, from an orphanage. Unbeknownst to Twilight, Anya is a test subject from a secret laboratory and can read minds, which she uses to navigate her new life while keeping her powers hidden. Next, Twilight marries Yor Briar, a seemingly ordinary office worker who is secretly an assassin codenamed Thorn Princess. Yor agrees to the marriage to maintain her cover, unaware of Twilight’s true identity. Together, the three form a family built on lies, each hiding their true selves while striving to maintain the facade.

The series explores the dynamics of this unconventional family as they navigate their dual lives. Twilight, despite his pragmatic approach, begins to develop genuine affection for Anya and Yor, complicating his mission. Anya, eager to please her new parents and avoid being sent back to the orphanage, uses her telepathy to assist Twilight in subtle ways, often leading to humorous and heartwarming situations. Yor, though initially distant, grows attached to her new family, even as her assassin duties occasionally interfere with her domestic life.

The plot unfolds through a mix of espionage, comedy, and slice-of-life elements. Twilight’s mission requires him to help Anya excel at Eden Academy, leading to various challenges, including school events, social interactions, and academic hurdles. Meanwhile, Yor’s assassin work occasionally brings danger to the family, forcing Twilight to balance his spy duties with protecting his loved ones. The series also delves into the broader political intrigue between Westalis and Ostania, with Twilight uncovering secrets that could impact the fragile peace between the two nations.

The main characters are defined by their unique traits and hidden identities. Twilight, or Loid Forger, is a master spy with exceptional combat skills, intelligence, and adaptability, but his emotional walls begin to crumble as he grows closer to his family. Anya, with her telepathic abilities, provides both comic relief and emotional depth, often serving as the bridge between Twilight and Yor. Yor, despite her deadly profession, is kind-hearted and struggles to balance her dual life, adding layers to her character. Together, they form a family that, while built on deception, gradually develops genuine bonds, creating a compelling narrative that blends action, humor, and heartfelt moments.