Rin Shinomiya, a third-year Kōetsu High student, holds authority as the Morals & Discipline Committee Chairperson. Her striking features—glossy black ponytail, chestnut-red eyes, and a beauty-mark beneath her right eye—complement her polished uniform of black tights and brown shoes, projecting an air of authority. Renowned for her poised composure and analytical mind, Rin garners admiration for her unwavering reliability and principled leadership. Yet beneath this disciplined exterior lies a playfully demanding streak, reserved solely for trusted companions—a testament to the martial arts discipline instilled by her grandfather, who honed both her spiritual arts expertise and unyielding resolve.

Rin's protective instincts shape key relationships: She formed an alliance with Wataru Sajou after he aided her friend Yuyu Inatomi, recognizing his integrity and often consulting him despite his refusal to join her committee. Her persistent efforts to reform delinquent first-year Kaede Sajou evolved into a steadfast camaraderie through Student Council collaborations. She dotes on the petite Yuyu, vigilantly shielding the fragile-looking underclassman while valuing their candid friendship.

The symbolism of her name reflects her essence—"Rin" (凛) evoking frosty dignity, while "Shinomiya" (四ノ宮) references fourth-ranked shrine traditions. This multifaceted persona has solidified her status as a respected figure, inspiring admiration across the student body.