I'm still looking for articles. I'll post what I know of for now.
http://www.boxrec.com/media/index.php?title=Fight:1379474
First in-ring death in Japan, apparently.
http://www.unifiedchamp.com/ucblog/?p=988Hundred of boxing people today (Thursday) attended a funeral service of Masatate Tsuji, Japanese top ranked 105-pound contender, who passed away on Tuesday because of brain hemorrhage after his come-from-behind defeat in a national elimination bout with Yuji Kanemitsu in Tokyo, Japan, last Saturday. Tsuji, 30, had swept almost all rounds before he abruptly succumbed in the tenth and final session. He was the thirty-fifth ring victim since the Japan Boxing Commission (JBC) was established just prior to the first world title bout between Dado Marino and Yoshio Shirai in 1952. It was a horrible shock wave to the Japanese boxing fraternity.
http://www.boxrec.com/media/index.php?title=Fight:1379474
First in-ring death in Japan, apparently.