Which publisher was the sole publisher of Sharaku's prints?

The publisher who was the sole publisher of Sharaku’s prints was Tsutaya Jūzaburō.

Tsutaya Jūzaburō was an Edo-period publisher whose career began in 1774 with illustrated guides to the Yoshiwara pleasure district. He later expanded into illustrated books, popular fiction, poetry anthologies, and ukiyo-e prints, becoming one of the most important cultural entrepreneurs of late-18th-century Edo.

For about ten months in 1794–1795, Tsutaya published the complete known body of work by the mysterious actor-print artist Tōshūsai Sharaku. Sharaku’s prints are celebrated for their striking, often unsparing portrayals of kabuki actors, and Tsutaya’s backing gave the artist access to skilled designers, carvers, and printers.

The word “publisher” can be misleading to modern readers. In ukiyo-e, the publisher commonly financed projects, commissioned designs, coordinated carving and printing, and marketed the finished sheets. Tsutaya also promoted Kitagawa Utamaro and supported writers including Santō Kyōden. Sharaku’s identity remains debated, but his publishing relationship with Tsutaya is well established.