Ichiko Ayase, the stern and unfriendly vice-president of her school's Student Council, secretly leads the Happiness Club under the alias "Kuraki." The club operates on a conviction that happiness is finite, compelling members to systematically harass and psychologically torment others to accrue "happiness points"—stealing joy under the delusion it enlarges their own share.

Her actions originate in profound trauma: after her older brother Kazuo killed himself following rejection by Shiraishi Kaori, Ichiko adopted a distorted worldview. Believing accumulated happiness points could metaphysically resurrect her deceased mother, she orchestrated a plan to gather the entire Happiness Club membership and burn them alive, aiming to harvest their collective happiness in one catastrophic event.

Her motivations intensify when Shiraishi reveals Kazuo died feeling fulfilled, shattering Ichiko's rationale. This disclosure exposes that Kazuo had emotionally "stolen" happiness from their family prior to his death, devastating Ichiko psychologically. Her belief system collapses, laying bare the futility of her actions.

In a confrontation with Shiraishi, Ichiko draws parallels between their experiences, implying shared culpability in perpetuating cycles of pain—a "Not So Different" dynamic underscoring their mutual entanglement in tragedy. Her arc concludes without redemption, marked by emotional dissolution as her constructed reality unravels.