Has 4 children with wife Megumi Matsumoto: Nobuhiro Ikehata, Tetsuo Yamashita, Mayuko Azusa, and actress Emi Ikehata.
Is considered to be the Japanese Frank Sinatra in his home country.
In March 2016, Kayama made a special art piece to commemorate 2,500,000 million downloads for the mobile game Terra Battle, that is featured as the background for the game's title screen.
As a guitarist, he took inspiration from the American instrumental group The Ventures, and performed a form of psychedelic surf music in the 1960s with his Mosrite guitar. One of his best-known instrumentals is "Black Sand Beach".
One of the last activities involves the song "Sarai", which he had written together with singer-songwriter Shinji Tanimura. The song was made as theme for the NTV charity program 24-Hr TV, and Kayama announced that 2022's edition of the program would be his last live performance of the song.
He showed his ability for drama when Akira Kurosawa cast him for his films Sanjuro and Red Beard.
Kayama rose to stardom in the 1960s in the Wakadaisho ("Young Guy") film series.
Kimi to Itsumademo" ("Love Forever"), another of his compositions, sold over two million copies, and was awarded a gold disc in 1965. At that point it was the biggest selling disc in the Japanese recording industry's history.
He announced that, by the end of 2022, he would be retiring from concert activities.