Hirayama created a new artistic realm with The Transmission of Buddhism and the continuing Buddhist Transmission series. Through these works, he grew increasingly interested in following the footsteps of the Buddhist master Xuanzang across the Silk Road, and in 1968, he and his wife Michiko traveled to this region for the first time—going to Afghanistan, India, and Central Asia. They later went to Iran, Syria, Turkey, China, Korea, and other areas along the Silk Road. In addition to this, Hirayama painted numerous masterpieces and taught many students as one of the leading professors at the Tokyo University of the Arts. In all, the Hirayamas made over 150 trips, from which Hirayama created as many as 600 sketchbooks from this part of the world.

During his travels, Hirayama Ikuo saw first hand the crisis facing invaluable cultural works due to wars and environmental destruction. Because of this, he called upon his many acquaintances to engage in the protection of cultural properties at Dunhuang in China, Angkor Wat in Cambodia, Bamiyan in Afghanistan, Koguryo on the Korean Peninsula, and other places around the world. In 1998, having received recognition both at home and abroad for his efforts in protecting cultural properties, Hirayama was awarded the Japanese Order of Cultural Merit, and held several offices such as the Director-General of Nihon Bijutsuin (the Japan Art Institute) and UNESCO Goodwill Ambassador until his death in December 2009. His various works and activities have left a deep and lasting impression on post-war Japanese culture.