Ichirō Satō adopted the persona "Maryuin Koga" during middle school, experiencing intense delusions where he acted as a fantasy hero. This chuunibyou phase triggered severe bullying and social isolation. It also caused significant family conflict, including physical punishment from his parents for his imaginary world and an imaginary girlfriend. His typically aloof and stoic elder sister provided his only familial moral support during this time, later confronting their parents about their inadequate response.

Seeking a fresh start, Ichirō transferred to a new high school. He deliberately suppressed his past fantasies to live as an ordinary student, though privately he found the world dull without them. His commitment to normalcy was tested when his teacher assigned him to support Ryōko Satō, a classmate exhibiting similar delusional behavior as an interdimensional researcher. Ichirō initially refused, fearing a relapse into his embarrassing past and further social rejection.

However, witnessing Ryōko endure bullying reminiscent of his own experiences prompted Ichirō to intervene. He gradually reconnected with his "Maryuin Koga" identity to protect her, forcing him to confront unresolved trauma and self-loathing. His commitment wavered when classmate Yumina Ōshima blackmailed him with details of his past, threatening exposure unless he abandoned Ryōko. This caused a temporary regression into self-doubt and withdrawal, negatively impacting Ryōko's mental state.

The crisis culminated when Ryōko retreated completely into her fantasy world, constructing an elaborate structure from school desks. Ichirō ultimately embraced his former persona fully, scaling the structure as "Maryuin Koga" to reach her. This act symbolized his acceptance of his past and demonstrated his commitment to guiding Ryōko toward reality without erasing her identity. Following this, he reconciled his family history, openly acknowledging his chuunibyou phase to his parents and peers. He formed genuine friendships with other socially marginalized students and committed to supporting Ryōko's gradual transition toward normalcy while maintaining a relationship with her. Mentors, including a teacher and a watch salesman, provided guidance throughout his journey.