"Ikkyu" is a historical manga series that centers on the life of Ikkyu Sojun, a real-life Zen Buddhist monk from 15th-century Japan. The narrative explores his journey from childhood to adulthood, highlighting his struggles, wisdom, and unconventional approach to life and spirituality. Born as the illegitimate son of Emperor Go-Komatsu, Ikkyu faces societal rejection and is sent to a monastery at a young age. Despite his royal lineage, he grows up in humble circumstances, developing a sharp intellect and a rebellious spirit.

The story delves into Ikkyu's formative years, depicting his rigorous training under various Zen masters and his eventual disillusionment with the rigid and often hypocritical practices of the monastic community. Ikkyu's quest for enlightenment leads him to embrace a more unorthodox path, blending profound spiritual insights with a playful, irreverent attitude. His interactions with common people, samurai, and fellow monks reveal his deep understanding of human nature and his ability to challenge societal norms through wit and wisdom.

Key characters include Ikkyu's mentors, such as Master Kaso, who recognizes his potential but struggles to contain his rebellious nature, and Yoso, a fellow monk who becomes both a rival and a friend. The series also features historical figures and fictional characters who cross paths with Ikkyu, each contributing to his growth and the broader exploration of themes like morality, authority, and the search for truth.

The plot is episodic, with each chapter often presenting a self-contained story that reflects Ikkyu's philosophical musings or his encounters with individuals from various walks of life. These vignettes collectively paint a portrait of a man who defies convention, using humor, poetry, and unconventional behavior to convey profound truths about existence and the human condition. The manga balances historical accuracy with creative storytelling, offering a nuanced portrayal of Ikkyu's legacy as a Zen master, poet, and cultural icon.