The emergence and development of the Obaku school of Chan (Zen) Buddhism is a momentous event in religious history, as important as the Bakufu's persecution of Christians, of the Tokugawa period. The Obaku's influence on Japanese culture goes beyond religion. The Obaku masters brought not only the late Ming and early Qing Buddhist teachings but also new art, crafts, lithography, and culture. The Obaku style became a distinctive one in Japanese art history. Its acculturation and assimilation in Japanese culture is also one of the important issues in the cultural exchange between China and Japan in the 17th century. This paper focuses on the images of Mt. Fuji and Buddhist masters in the poetry of the second Obaku patriarch, Muan. It probes the changes in Muan's mentality after he arrived in Japan. Mt. Fuji is a recurrent image in Muan's poems. His depiction of it was based on hearsay and imagination at first. However, it became more nuanced after he traveled to Edo. Mt. Fuji became then a metaphor with rich meaning, communicating the process of Muan's assimilation into Japanese society. As for the hymns to the Japanese Buddhist masters, those works showed that Muan placed himself among them, constructing therein a shared tradition of Zen Buddhism between China and Japan. This paper also explores the literary element in the Obaku tradition, considering the interactions between poetry and Zen Buddhism. Finally, it examines how the Obaku sect faced, accepted, and assimilated the Japanese Buddhist tradition to create a new, distinctive religious and cultural system.