Yōsō Sōi was a historical Zen Buddhist monk, a contemporary of Ikkyū Sōjun during Japan's Muromachi period. He trained alongside Ikkyū under the Zen master Kasō Sōdon at a hermitage on Lake Biwa in the early 15th century. Yōsō Sōi later rose to become the 26th head priest of Kyoto's Daitokuji temple, securing his place within the formal monastic hierarchy.

Artistic portrayals show Yōsō Sōi witnessing Ikkyū Sōjun's unconventional behavior, such as singing karaoke with a microphone amidst his lover and followers. In these scenes, Yōsō Sōi and fellow conservative priests react visibly with envy to Ikkyū's irreverent yet charismatic displays. This juxtaposition casts Yōsō Sōi as a representative of traditional monastic values, frequently positioned in opposition to Ikkyū's rejection of religious precepts and societal norms.

His dynamic with Ikkyū underscores the tension between institutional Buddhism and individual expression within Zen practice of their era.