Born the eldest son of the low-class aristocratic Ukitake family, Jūshirō Ukitake carried responsibility for supporting five brothers and two sisters. At age three, he contracted a fatal lung disease that turned his hair white. After doctors abandoned his case, his parents brought him to the shrine of Mimihagi in Rukongai's 76th Eastern District. Mimihagi, later revealed as the Soul King's Right Arm governing "Stillness," symbiotically saved him by taking his diseased lungs. This left Ukitake with perpetually fragile health, suffering recurrent illness and coughing blood throughout his life. He trained under Captain-Commander Yamamoto at Shin'ō Academy, becoming one of its first graduates alongside Shunsui Kyōraku. Both achieved captaincy in the Gotei 13 earlier than any other graduates. Alongside Yamamoto, Retsu Unohana, and Kyōraku, Ukitake ranks among the longest-serving captains, holding his position for over a century by events 110 years prior to the main storyline. Yamamoto personally instructed him, solidifying his foundational combat and leadership skills. As Captain of the 13th Division, Ukitake appointed Kaien Shiba as his lieutenant. When Kaien's wife Miyako died battling a Hollow, Kaien sought vengeance. Ukitake permitted him to confront the Hollow alone, accompanied by Rukia Kuchiki. After the Hollow possessed Kaien, Ukitake intervened but was hindered by his illness. Kaien ultimately impaled himself on Rukia's blade to preserve his honor. Ukitake subsequently refused to appoint a new lieutenant, citing Kaien as irreplaceable; he delegated duties to third seats Kiyone Kotetsu and Sentarō Kotsubaki instead. Ukitake played key roles in critical events. He opposed Central 46's orders during Rukia Kuchiki's scheduled execution, collaborating with Kyōraku to unseal the Shihōin Shield and destroy the Sōkyoku to halt the process. He later intervened to protect Ganju Shiba and Hanatarō Yamada from Captain Byakuya Kuchiki. Against the Espada, he spared Lilynette Gingerbuck and advised her to leave the battlefield. During the Thousand-Year Blood War, Ukitake's connection to Mimihagi became central. Aware of Yhwach's plan to kill the Soul King and destabilize existence, he retreated to Mimihagi's shrine during the Quincy invasion. There, he initiated the Kamikake ritual, merging fully with Mimihagi to become the new vessel for the Soul King's Right Arm. This sacrifice stabilized reality temporarily after Yhwach destroyed the Soul King, costing Ukitake his life. Ukitake possessed immense Reiatsu, enabling him to withstand Yamamoto's attacks and effortlessly block Lilynette's Cero. His Zanpakutō, Sōgyo no Kotowari, released via the command "All Ye Waves, Become My Shield. All Ye Thunder, Become My Blade," could absorb and redirect energy-based attacks. He also mastered Kidō, aiding in complex operations like resealing the Jōkaishō and opening the Senkaimon. Personality-wise, Ukitake prioritized protecting others over rules or personal safety. He treated everyone with respect regardless of rank, often offering advice or aid. He avoided harming children, even enemies, and upheld honor in combat. His actions—refusing a new lieutenant to prevent further loss and sacrificing himself for cosmic balance—reflected his core belief: preserving life outweighed all else.