Loid Forger, known by his code name Twilight, is the main protagonist of the story. He is a highly skilled spy working for WISE, the Westalian intelligence service. His true name and exact age are unknown, as he discarded his original identity when he became a spy. Twilight grew up in Luwen, a town in Westalis near the border with Ostania. During his childhood, a war broke out that destroyed his hometown, killed his close friends, and separated him from his parents. This traumatic experience gave him a deep resolve to prevent war and create a world where children do not have to cry. After the war, he enlisted in the army under a false name, eventually being recruited into WISE and trained in espionage under an officer named Sylvia Sherwood.

Twilight is intelligent, composed, and extraordinarily capable. He possesses genius-level intellect, eidetic memory, masterful skills in disguise, expert marksmanship, and advanced hand-to-hand combat abilities. He is also a meticulous planner who can process information at high speed and adapt to rapidly changing situations. Despite his cold professionalism, he has a strong moral core and a sincere desire to protect peace. Over the course of the story, he reveals a softer, more vulnerable side, particularly in his interactions with his family, though he often frames his growing care for them in terms of mission necessity.

His primary motivation is completing Operation Strix, the mission assigned to him by WISE. The goal of Operation Strix is to get close to Donovan Desmond, a reclusive Ostanian politician whose policies threaten the fragile peace between East and West. Because Desmond is almost impossible to approach directly, the only feasible method is for Twilight to enroll a child in the same elite school as Desmond's son, Damian, and pose as a fellow parent. To create this cover, he adopts the identity of Loid Forger, a psychiatrist at Berlint General Hospital, and constructs a fake family.

The role Loid plays in the story is that of the orchestrator and caretaker of the Forger family, while also secretly advancing his espionage mission. He is the one who initiates the creation of the family as a tactical asset, adopting Anya from an orphanage and entering into a marriage of convenience with Yor Briar. Throughout the narrative, he juggles his spy duties with the demands of family life, often finding that the chaos of domesticity is far more unpredictable than any mission.

His key relationships are central to the story. Anya Forger, his adopted daughter, is a telepath who can read minds. Loid does not know about her ability, and she is the only one who knows the true identities of both her parents. Despite his initial view of her as a mission component, Loid gradually develops genuine paternal affection for her, becoming protective and caring in ways that go beyond the requirements of the job. Yor Forger, his wife, is a city hall clerk by day and a professional assassin known as the Thorn Princess by night. Loid is unaware of her secret, and she does not know he is a spy. The marriage is initially a practical arrangement for both, but over time, Loid’s feelings for Yor become more authentic, and he finds himself concerned for her safety and happiness in a way that transcends the mission. Bond Forger, the family’s large dog, can see glimpses of the future. Loid adopts Bond and trains him as a guard dog, unaware of his precognitive abilities. Franky Franklin, a local informant, is Loid’s occasional ally and friend who provides support and comic relief. Fiona Frost, a junior colleague from WISE, is a skilled agent who harbors romantic feelings for Loid and is jealous of Yor; Loid is unaware of the depth of her infatuation. Sylvia Sherwood is his direct handler in WISE, who assigns Operation Strix and monitors its progress, maintaining a professional but supportive relationship with Loid.

Loid undergoes notable development over the course of the series. Initially, he is entirely mission-focused, viewing Anya and Yor as assets to be managed. He is emotionally reserved, rarely showing vulnerability. However, as he experiences genuine moments of connection and care with his family, he begins to question his own detachment. His ideals about preventing war and protecting children take on a personal dimension as he finds himself wanting to preserve the peace and happiness he has built with them. His growth is shown in the gradual softening of his demeanor, his increasing willingness to admit he cares, and his internal conflict between his spy instincts and his emerging family bonds.

His notable abilities are extensive and reflect his elite training. He is a master of disguise, capable of altering his appearance and voice to impersonate anyone. He has peak physical conditioning, enabling him to overpower multiple opponents. He is an expert marksman and highly skilled in hand-to-hand combat. His strategic mind allows him to plan complex operations and adapt quickly. He also has a high tolerance for alcohol and is proficient in a wide range of practical skills, from cooking to tennis, all of which he uses in his various cover roles. However, despite his competence as a spy, he sometimes struggles with the unpredictability of family life and can be oblivious to things that fall outside his professional framework, such as Yor’s superhuman feats or the true nature of Anya’s abilities.