Choromatsu Matsuno is the third-born of the Matsuno sextuplets. His name originates from an Edo-era term for "fast-running and foolish children" combined with the onomatopoeia "chorochoro" (to rush). In childhood, he was quick to judge and quick to flee, known as the fastest brother and skilled in agility-based sports. He possessed a fiery temper and prioritized results over his brothers' well-being. Choromatsu frequently partnered with Osomatsu, though their relationship involved rivalry and power struggles; he once temporarily assumed leadership during Osomatsu's absence, becoming domineering until Osomatsu returned. Certain childhood incidents depicted him as unlucky, like being urinated on by an elephant, or becoming flustered when spotlighted. As a teenager, Choromatsu adopted thick glasses to project studiousness but concealed erotic magazines in textbooks, resulting in poor grades. His posture and movements became noticeably stiff by age 18. In adulthood, Choromatsu positions himself as the most logical and responsible brother, frequently expressing concern over the sextuplets' unemployment and NEET lifestyle. He often serves as the straight man to his siblings' antics and advocates for maturity, even suggesting he should replace Osomatsu as the eldest. However, this self-image is contradicted by his obsessive idol fandom focused on Totoko and Nyaa-chan; he admits his interest stems from fantasizing about the idols rather than their music. His attempts at responsibility are frequently undermined by his own complacency or external circumstances, reverting him to NEET behavior. Physically, his adult design features smaller pupils, a triangular downturned mouth, and no cowlicks, typically wearing green-themed clothing. During the adventure for the legendary shining fruit, Choromatsu joined Osomatsu in rallying their brothers to fight a tyrannosaurus, proclaiming unity. After encountering the Hipipo Tribe, he was the first to attempt farming with their tools despite struggling with the heavy hoe, eventually collaborating with his brothers on crop cultivation and house-building. When a hurricane destroyed their efforts, he regained determination by observing the tribe's resilience. In the climax, he participated in retrieving the fruit, explained its life-changing potential to the world, and joined his brothers in consuming it, transforming them into Hipipo-like creatures.