Koben was busshi (sculptor of Buddhist Statues) in the Kamakura period. He was a third son of Unkei. He once shared the task of sculpting Kongo Rikishi zo (statue of Kongo Rikishi (Nio)) flanked with Nandaimon gate of To-ji Temple and statues in Hokuen-do hall of Kofuku-ji Temple.
Koben sculpted the 'standing statue of Ryutoki' in the Kofuku-ji Temple.
The sculpture was Ryutoki (dwarf daemon) bearing Toro (lantern) on his head with his arms folded and was paired with the 'standing statue of Tentoki.'
The sculptor of Tentoki is unknown.