Ken Sugisaki, a second-year Hekiyou Academy student, holds the vice-presidency for both the 32nd and 33rd Student Councils. He secured his position via the "blue chip" seat, awarded to the top-scoring student, after an extraordinary academic climb from nearly the bottom of his class. This transformation was fueled by intense study motivated solely by his ambition to join the student council.

Separated from his mother early in life, Ken lived with his father near childhood friend Asuka Matsubara. Following his father's remarriage, he gained a stepsister, Ringo Sugisaki, forging a strong non-blood-related bond. Ken's subsequent romantic relationship with Asuka in middle school triggered Ringo's extreme self-harm reaction and hospitalization. The breakup and false rumors of him two-timing led to prolonged bullying, which Ken accepted as deserved punishment.

Ken cultivates a perverted, harem-seeking persona, openly declaring his intent to turn the student council into his harem and indulging in eroge games. This behavior frequently invites physical or verbal retaliation. Behind this facade lies a diligent worker who routinely shoulders all council duties alone, enabling other members to relax. He demonstrates genuine care, willingly assisting those in need and displaying protective instincts, such as jealousy towards males interacting with council members. His inherent charisma ensures no genuine dislike for him exists at school.

His motivations are rooted in past trauma. Each council member aided him during his difficult first year, leading him to view the council as his cherished "dream." He strives to repay them by safeguarding their collective happiness. His overt perversion and harem goal function as defense mechanisms against romantic attachments, stemming from guilt over the Ringo incident and fear of repeating past failures. This manifests in surprise and distress when confronted with confessions, like Kurimu Sakurano's admission of love.

Ken's character evolves across official media. Initially fixated on creating a carefree harem, he gradually confronts deeper emotions. By the seventh light novel volume, Kurimu recognizes her romantic feelings but hesitates. She confesses in the ninth volume, and Ken reciprocates, acknowledging unique feelings for her. They begin dating, though he clings to his harem rhetoric as emotional protection. Later storylines explore his interactions with Ringo, including an incident where the council searches for him after her frantic call reporting his kidnapping.

A dedicated episode delves into Ken's backstory, recalling the arduous efforts leading to his academic success and council membership. His relationship with the council culminates in a final chance to express his true feelings before members graduate or transfer.

Etymologically, his surname Sugisaki combines "cedar" (杉) and "cape/peninsula" (崎), while Ken (鍵) means "key," earning him the nickname "Key-kun."