Eishiro Sugata, disowned by his prominent political family following his older brother's fatal glider accident – an event he blamed on his own lapse during a pre-flight argument – dedicated his life to discovering a "New World" as atonement. He established the New World Discovery Club at Sorami High School to pursue this goal. Living austerely near a river and wearing only his school uniform, he drew inspiration from historical explorers like Magellan and Columbus.

Sugata consistently displayed a calm, analytical demeanor coupled with exceptional intellect and combat prowess equal to his childhood friend, Mikako Satsukitane. His scientific focus centered on investigating Synapse, the realm he identified as the "New World," and its Angeloid inhabitants, often employing eccentric methods such as using assistants nicknamed "Pretty-kun," which ranged from a Barbie doll to a live trout. Despite maintaining a neutral expression, he demonstrated fierce loyalty to friends, particularly Tomoki Sakurai, whom he mentored.

In *The Angeloid of Clockwork* movie, Sugata played a critical role when Hiyori Kazane sought to join his club. He initially opposed her inclusion due to her resemblance to an Angeloid in Synapse but relented after Mikako cited budgetary benefits. As Hiyori integrated into the group, Sugata collaborated with Daedalus in Synapse to investigate her connection to the Angeloid and the memory-altering phenomena affecting humans encountering Synapse entities. After Hiyori's death and subsequent erasure from collective memory, Sugata desperately rushed to Synapse to identify her among the Angeloids in stasis pods but failed to retain his memories after the Master of Synapse intervened. His efforts to preserve Hiyori's existence proved futile due to the memory wipe.

Sugata appeared in spin-offs like *Yūryō Bukken Mō Dame Sō*, where his younger brother Yuugo was revealed as the family heir. Yuugo recognized Hamuel, a character resembling Sugata's deceased childhood friend, prompting Sugata to contact him and reveal his prior knowledge of Synapse's secrets, confirming his ongoing investigations across media.

His character development included high-stakes sacrifices, such as risking his life to reprogram Synapse's Rule Obelisk during the manga's final arc, an act that seemingly resulted in his death until Tomoki's wish restored him. His intellectual contributions remained pivotal throughout the series, including impressing the Master of Synapse and aiding in critical battles against Angeloid threats.