"Otona no Ikkyū-san" is a historical anime series that reimagines the life of Ikkyū Sōjun, a renowned Zen Buddhist monk from 15th-century Japan. The narrative explores Ikkyū's adult years, blending historical events with fictionalized elements to depict his philosophical journey, personal struggles, and interactions with the societal and political landscape of his time. The series delves into Ikkyū's unconventional approach to Zen Buddhism, emphasizing his rejection of rigid monastic practices and his embrace of a more humanistic, free-spirited philosophy. His character is portrayed as a complex figure, balancing his spiritual pursuits with a deep connection to the everyday lives of ordinary people.

The plot revolves around Ikkyū's efforts to navigate the tensions between the ruling class and the common folk, often using his wit and wisdom to mediate conflicts or challenge corrupt authority. His relationships with various characters, including fellow monks, political figures, and ordinary citizens, highlight his multifaceted personality and his commitment to justice and compassion. The series also explores Ikkyū's internal conflicts, particularly his struggles with desire, attachment, and the contradictions inherent in his role as a spiritual leader.

Key supporting characters include Ikkyū's mentor, who represents traditional Zen ideals, and a range of historical and fictional figures who provide contrasting perspectives on morality, power, and spirituality. The narrative is episodic in nature, with each episode often focusing on a specific moral dilemma or philosophical question, allowing for a nuanced exploration of Ikkyū's teachings and their broader implications. Through its portrayal of Ikkyū's life, the series offers a thoughtful examination of Zen Buddhism, human nature, and the complexities of living a meaningful life in a turbulent world.