Eldest son of the sage-king Yao and the heir he passed over. Judged unworthy by the Shiji, Danzhu is the foil whose unfitness motivates Yao's abdication to the meritorious commoner Shun — the foundational case-study of merit-over-bloodline succession in Confucian political theory (Mencius 5A.5-6). After Yao's death Shun ritually yielded to Danzhu, but the people turned to Shun, confirming Heaven's choice. A later tradition (Bowuzhi) credits Yao with inventing weiqi to instruct him. Named in chinese_yao's lifecycle ('abdicated to Shun rather than to his own son Danzhu') until materialized here as the paternal-line son.