In 1948, he won the biggest amateur Go tournament in Japan, the All-Amateur Honinbo.
For two years straight, Kageyama was runner up for the Prime Minister Cup.
[1] The greatest accomplishment of his life, in his own opinion, was beating Rin Kaiho in the Prime Minister Cup semi-finals.
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.
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.