Kageyama was born in Shizuoka Prefecture, Japan. In 1948, he won the biggest amateur Go tournament in Japan, the All-Amateur Honinbo. The year after that, he passed the pro exam.
For two years straight, Kageyama was runner up for the Prime Minister Cup. First, against Otake Hideo, then Hoshino Toshi. His style was a very calm one with deep calculations, similar to what Ishida Yoshio would use later on. The greatest accomplishment of his life, in his own opinion, was beating Rin Kaiho in the Prime Minister Cup semi-finals. At the time, Rin was the Meijin, the top player in Japan. Kageyama gave a commentary on this game in his book "Lessons in the Fundamentals of Go", where he wrote
Experiences like the following are what make it impossible to stop playing Go. The year was 1965. I had advanced to the semifinals of the Prime Minister Cup, and in the semifinal game I scored the upset of my life by beating the current Meijin, Rin Kaiho. Even now the memory is so intoxicating that I am embarrassed to think what this commentary is going to sound like, but I don't care. This game is one of my lifetime masterpieces.