Seijuurou Shin 

• Birthday: July 9th
• Age: 17-18 (series run), 20 (post-series)
• Height: 5'8" (175cm)
• Weight: 156 lbs (71kg)
• Prior Teams: Oujou White Knights, Team Japan
• Current Team: Oujou Silver Knights
• Main Position: linebacker (LB)
• Jersey Number: 40
• 40-yard Dash: 4.36 seconds
• Benchpress: 308.65 lbs (140kg)

Seijuurou Shin is Sena Kobayakawa's first-ever rival in American football. For most of Eyeshield 21, he is a second-year student at Oujou High School and ace linebacker for the Oujou White Knights, Tokyo's leading defensive American football team.

Stoic and cool-headed, Shin's main focus is strengthening his physique, often to the point that he's not good at focusing on much else. He has bare-minimum social skills and cannot read the room very well, so he can come off cold or awkward when interacting his teammates. He also can't comprehend technology, and quickly forgets his own strength when confronted with it. So any gadget or hardware that Shin touches breaks into pieces within a few seconds.

All of this said, Shin is an unshakable genius when it comes to athletics. Thanks to his tireless training and exercise, Shin is incredibly muscular and possesses quick reflexes, making him nearly unmatched in both strength and speed. This allows him to tackle with one hand from a long distance, causing any of his targets terrible pain on-contact. He can even identify people's abilities by merely observing their physical builds, though he hardly ever notices their faces.

Although Shin's character changes very little throughout the story, his strength, speed, and techniques all steadily increase alongside Sena's. Sena outrunning him was his first experience with "the world of light-speed," as he sometimes calls it. So their rivalry provides Shin with both a welcome challenge and a newfound enjoyment for American football that he hasn't felt in a long time.

By the end of the series, Shin is a sophomore at Oujou University and linebacker for their team, the Oujou Silver Knights.