Ken emerges as the central antagonist, spearheading the "Yesterday Once More" initiative to forcibly return society to the 20th century, driven by revulsion toward the 21st century’s perceived moral decay and emotional desolation. His crusade, rooted in an obsessive nostalgia for an era he deems spiritually purer, unfolds alongside his devoted partner Chaco. Both don head-to-toe black attire, retro hairstyles, and vintage accessories as deliberate rejections of contemporary aesthetics.

To achieve his vision, Ken deploys a scent-based system that floods adults’ senses with vivid 20th-century memories, compelling them to shed adult responsibilities and regress into childlike states. This olfactory weapon disperses from a machine concealed within a nostalgia-themed expo—a meticulously crafted trap designed to imprison participants in an illusory past. While dispatching henchmen to apprehend rebellious children, Ken himself avoids brute force, preferring psychological warfare and environmental control to enforce his ideals.

His reverence for the past manifests in tangible symbols: a cherry-red Toyota 2000GT he calls his "soulmate," recurrent echoes of The Carpenters’ melancholic anthem in the project’s operations, and a persona blending John Lennon’s countercultural flair with dogmatic devotion to bygone norms.

When the plan collapses, Ken attempts a joint suicide with Chaco, only to be interrupted by a nesting pigeon—a metaphor for familial resilience and temporal progression. Though this confrontation forces his begrudging acknowledgment of the present, his capacity to adapt lingers unresolved, leaving his fate entwined with unanswered questions.