Katsumi Kureko works as a scriptwriter for the MRS radio channel, collaborating with colleagues Kanetsugu Mato and Madoka Chishiro. Sporting ashy blond hair and a slender mustache, he often dons a yellow shirt and gray pants. His first notable appearance occurs during Minare Koda’s rogue broadcast, where he approves airing her recording by citing the time slot’s amateur designation, though he later voices legal concerns before deferring to Mato’s decision. Outside radio, he pens erotic fiction under the pseudonym Hisaki Kure.

A long-standing friendship with Mato leads him to occasionally craft scripts for Minare’s show despite his primary commitment to Madoka’s program. His role thrusts him into peril when cultists seize him and others during the School of Wave Wisdom incident, aiming to exploit radio frequencies. Frequent collaborations with Madoka imply an undefined personal rapport beyond their professional dynamic.

His given name, derived from “overcome” and “three” (克三), contrasts his surname’s amalgamation of “long time,” “communicating,” and “tree” (久連木), reflecting layers of his identity within the narrative’s framework.