Kohaku, a young woman of Ishigami Village, exists 3,700 years after humanity’s global petrification. Descended from survivors Byakuya Ishigami and Lillian Weinberg, she is the daughter of Kokuyo and younger sister of Ruri, the ailing village priestess. Her striking features—blonde spiky ponytail, piercing blue eyes, and athletic frame—complement her practical attire: a sleeveless navy dress with a rope belt, stone sandals, and a ribbon choker mirroring Lillian’s. Dedicated to sustaining her sister’s fragile health, Kohaku spent years delivering therapeutic hot spring water while defiantly rejecting the priestess mantle to preserve Ruri’s purpose. Her rebellious spirit drew her to Senku, whose scientific brilliance and resolve to revive civilization inspired her to ally with him. She strategically bridged his innovations with her village, mobilizing resistance against Tsukasa’s tyranny. Renowned for unmatched agility and combat mastery, Kohaku anchors the Kingdom of Science’s Power Team, scavenging resources, shielding allies, and outmaneuvering foes like Hyoga and Homura. Though a fierce warrior, she staunchly avoids lethal force unless sanctioned by her allies. Her loyalty intertwines with impulsiveness, driving her to spar playfully, mentor the orphaned Suika, and aid Chrome’s earnest courtship of Ruri. Initially wary of outsiders like Gen, she pragmatically collaborates with them when village interests align. Kohaku’s bond with Senku balances reverence with tactical partnership. She openly admires his relentless pursuit of progress, framing her romantic ideals around his steadfastness. Their dynamic peaks during high-stakes gambits, such as her feigned kiss to distract enemies on Treasure Island or their wordless embrace after surviving catastrophe. While Senku prioritizes rebuilding society, their synergy underscores unspoken trust. Across pivotal arcs—from Village Games strategizing to crafting cellphone networks and confronting the Petrification Kingdom—Kohaku adapts ancestral survival wisdom to Senku’s scientific vision. She navigates oil rigs and deciphers Byakuya’s time capsule, intertwining heritage with innovation. Her journey reflects a bridge between ancient traditions and futuristic ambition, eternally guarding both family and humanity’s rebirth with equal ferocity.