Xu Xian is a human character from Chinese folklore, specifically the Legend of the White Snake, adapted across various media including anime. His background and development are detailed below. In Song-dynasty China, Xu Xian lived in Lin'an Prefecture (modern Hangzhou) as a scholar or physician. One origin story recounts him unknowingly consuming immortality pills sold by the immortal Lü Dongbin near West Lake's Broken Bridge; he vomited the pills into the lake, where a white snake spirit (Bai Suzhen) consumed them, gaining 500 years of magical power and linking their destinies. An alternate origin describes Xu Xian saving a white snake in a past life, prompting Bai Suzhen to seek him for repayment. During the Qingming Festival, Xu Xian encountered Bai Suzhen and her companion Xiaoqing (a green snake spirit) on the Broken Bridge in the rain. He lent them his umbrella, sparking their romance. They married and ran a successful herbal medicine shop aided by Bai Suzhen's supernatural abilities. Their peace shattered when the Buddhist monk Fahai revealed Bai Suzhen's true identity to Xu Xian. Following Fahai's counsel, Xu Xian tricked Bai Suzhen into drinking realgar wine during the Dragon Boat Festival, causing her to revert to her snake form; Xu Xian died of shock upon seeing the transformation. To resurrect Xu Xian, Bai Suzhen retrieved a magical herb from Mount Emei or Kunlun, overcoming guardians like the Deer Boy and White Crane Boy. The Old Man of the South Pole granted her the herb out of pity. Revived, Xu Xian felt fear but ultimately acknowledged his enduring love for Bai Suzhen, accepting her non-human nature. Fahai then imprisoned Xu Xian at Jinshan Temple for his "protection." Bai Suzhen and Xiaoqing flooded the temple to rescue him, causing collateral damage. During the conflict, Xu Xian confirmed his loyalty to Bai Suzhen and escaped with help from a sympathetic monk. Reunited with Bai Suzhen on the Broken Bridge, Xu Xian apologized. Xiaoqing's initial fury subsided due to Bai Suzhen's forgiveness. Bai Suzhen later gave birth to their son, Xu Shilin (or Xu Mengjiao). Fahai captured Bai Suzhen, imprisoning her under Leifeng Pagoda. Xu Xian became a monk at Jinshan Temple or Zhaoging Monastery, adopting the name "Daozong." He remained there until restlessness led him to depart, leaving his sister-in-law to raise Xu Shilin. Decades later, Xu Shilin excelled academically, becoming the top scholar (Zhuangyuan) in the imperial examinations. He petitioned the emperor to free his mother, resulting in an official tribute at Leifeng Pagoda. Some versions depict his filial piety causing the pagoda to collapse, releasing Bai Suzhen. Alternate endings show Xu Shilin briefly reuniting with Bai Suzhen before her ascension to heaven or the family achieving full reconciliation. In the 2019 anime film adaptation, Xu Xian (named Xu Xuan) is reimagined as a young herb collector from a snake-hunting village. Despite fearing snakes, he protected Bai Suzhen (Xiao-Bai) after she saved him. He demonstrated knowledge of medicine and occult practices (Qimen Dunjia), using these skills to aid her. Intervention by a Fox Fairy temporarily transformed him into a demon, enhancing his physical abilities but permanently nullifying his potential for magical cultivation. This iteration emphasizes his moral alignment, judging others by actions rather than species. Xu Xian's character evolves from a naive human susceptible to external manipulation to a figure of steadfast love and acceptance. His narrative consistently explores themes of transcending prejudice and fulfilling karmic bonds.