Eishirou Sugata, a tall, slender figure with light gray hair and blue-green eyes framed by rectangular glasses, perpetually wears his school uniform, lacking alternative attire. His composed exterior masks an eccentric intellect and relentless curiosity as president of the New World Discovery Club, where he investigates the enigmatic "New World" phenomenon and Synapse’s Angeloids. Driven by guilt over his older brother’s fatal glider accident—caused by an undetected wing malfunction during their argument—Eishirou seeks redemption after being disowned, leaving his family’s heirship to younger brother Yuugo.

Residing in a riverside tent, he employs unorthodox tools: a Barbie doll and live trout, both dubbed "Pretty-kun," to probe mysteries involving Tomoki Sakurai and Angeloids like Ikaros. Though methodical, his homemade experiments, including glider tests, often spiral into chaos. His complex dynamic with Mikako Satsukitane blends rivalry and mutual respect, underscored by her family’s deference to him as "young master." Equally skilled in combat, Eishirou allies with Synapse’s Daedalus, earning the realm’s ruler’s esteem for his ingenuity.

Pivotal contributions include sheltering Astraea, dissecting Angeloid technology, and doubting Ikaros’ Pet-Class designation. During the Chaos arc, he scorns destructive Angeloids yet shields allies, culminating in a sacrificial infiltration of Synapse to reprogram the Rule Obelisk. Presumed dead, he resurfaces post-reality reset triggered by Tomoki’s wish. Spin-offs like *Dame Sō* depict an older Eishirou contacting heir Yuugo to expose Synapse’s secrets, while *Yūryō Bukken Mō Dame Sō* ties his legacy to Yuugo’s encounter with Hamuel, a figure echoing his past.

Eishirou’s journey balances scientific rigor with emotional growth, tempered by friendship with Tomoki that redirects his nihilism toward preservation. His evolution—from atoning for his brother’s death to bridging humanity and Synapse—hinges on relentless inquiry, quiet resolve, and the interplay of intellect and guilt, cementing his role as both outcast and visionary.