"This Girlfriend is a Fiction" centers on the life of a high school student, Yuuto Kirishima, who struggles with social anxiety and a lack of confidence. To cope with his loneliness and the pressure to fit in, he fabricates a story about having a girlfriend, creating an idealized version of a romantic partner named Rina. This fictional girlfriend becomes a central part of his daily life as he shares fabricated stories about her with his classmates, who believe she is real. However, Yuuto’s lies begin to unravel when a new transfer student, Rina Aizawa, arrives at his school. Coincidentally, she shares the same name as his imaginary girlfriend and bears a striking resemblance to the girl he described.

Rina Aizawa, intrigued by Yuuto’s stories, decides to play along and pretends to be his fictional girlfriend. As the two interact, their relationship evolves into a complex dynamic filled with humor, misunderstandings, and emotional growth. Rina’s decision to go along with Yuuto’s fabrication forces him to confront his insecurities and the consequences of his lies. The story explores themes of self-acceptance, the nature of truth, and the challenges of forming genuine connections.

The narrative delves into the lives of supporting characters, including Yuuto’s classmates and friends, who become entangled in the web of his deception. Their reactions and interactions add depth to the story, highlighting the impact of Yuuto’s actions on those around him. As the series progresses, the line between fiction and reality blurs, leading to moments of introspection and character development for both Yuuto and Rina. The manga balances comedic elements with heartfelt moments, creating a story that is both entertaining and thought-provoking.