You didn´t include Hasegawa. From my time as a fan he was the strongest japanese name anda rarely remembered. Jiro Watanabe was pretty good too, but I guess he is not forgotten ?
Out of the fighters listed I would say Kuniaki Shibata. Very talented fighter but pretty fragile all round. Hiroyuki Ebihara needs to be on the list. Should be in the HOF in my personal opinion. Shozo Saijo should also be mentioned as well. Largely forgotten champion who were very talented. Fast hands, aggressive and very good boxing skills. Like Shibata he had a pretty fragile chin.
Not the most talented fighter by any means but I think Takuya Muguruma is an almost forgotten Japanese champion who was always exciting. His fight with Wilfredo Vazquez is fantastic.