Rena Ryūgū, originally named Reina Ryūgū, emerges as a pivotal character shaped by familial dissolution and psychological turmoil. Her parents’ divorce, spurred by her mother’s infidelity, precipitated a violent mental collapse during which she assaulted peers, vandalized school property, and attempted self-harm under the delusion of maggots infesting her bloodstream. This crisis stemmed from undiagnosed Hinamizawa Syndrome, a disorder manifesting paranoia and hallucinations. Returning to her hometown, she shed her birth name, excising the “i” from Reina to escape associations with “icky” past trauma, though she later grappled with losing positive ties to the original spelling. Driven by an obsession to hoard “cute” items, she intermittently enters “Cute Mode,” a fervent state fixated on claiming objects—often from friends like Rika and Satoko—through relentless determination. This compulsion contrasts her sharp perceptiveness, enabling her to unravel concealed truths from scant clues. Her fierce loyalty to companions coexists with a volatile rejection of deceit, erupting in the iconic cry “Uso da!” when confronting lies. Protecting her father from manipulative schemes forms a core motivator, culminating in the calculated killings of Rina and Teppei. She disposes of their remains with chilling precision, revealing a strategic, ruthless facet. Yet remorse surfaces, notably when Keiichi intervenes during a school hostage crisis where she planned mass murder-suicide. Adult iterations depict Rena attending university, retaining her idiosyncratic traits, and later mothering a son, Kihiro, referenced in 2019-era narratives. Her steadfast belief in Oyashiro-sama’s curse persistently molds her decisions and relationships. A cleaver, repurposed from a gardening tool, embodies her dual role as guardian and threat. Her arc intertwines resilience and fragility, oscillating between whimsical “Cute Mode” antics and harrowing psychological struggles. The tension between her bubbly exterior and latent violence underscores themes of trauma and endurance, anchoring her actions in a past marred by instability and unresolved mental strife.