Kou Kurou is the youngest brother of Kou Shouka and Kou Reishin in the Kou (Crimson) Clan. He functions as the proxy head, a role held so long many outsiders mistake him for the clan's true leader instead of Reishin. Kurou prioritizes tradition and family loyalty above all. He influenced their father to bypass Shouka as clan successor in favor of Reishin, deeming Shouka unfit. Yet, Kurou fiercely defends the clan's honor. When servants exploited Shouka's grief after his wife Shoukun's death to steal household valuables, Kurou ordered the thieves found and subjected to severe torture, sending their severed ears and eyes to their families as a stark warning against harming the Kou family. He maintains the clan's Hong Province operations with his wife Kyuuka and their children, Kou Hakuyuu and Kou Sera. Unbeknownst to his niece Shuurei, Kurou travels to the capital to extend the Kou clan's protection when she becomes an imperial official. When Reishin faces accusations of manipulating exam results for Shuurei, Kurou protests by ordering clan members to cease work, halting half the country's functions. Kurou intervenes again during Shuurei's appointment as co-governor of Sa Province. The travel pass issued by Ko Kijin (Yellow Clan) minister bears the Kou clan's distinctive "seven-colored ink," marking Shuurei as under their protection. He intends for Shuurei and his nephew Li Kouyuu (Reishin's adopted son) to marry and lead the clan. To this end, he trains his son Hakuyuu from birth to be Kouyuu's future assistant. However, Reishin rejects marriage proposals between Shuurei and Hakuyuu, citing concerns Hakuyuu "might meet a girl and run away with her at any given moment."