I noticed you are in Tokyo, any chance you've found any of the operating systems that were released for the Japanese Model I with the Kana keyboard and ROMs?
Is the Japanese Model I the TEC with the Kana keyboard? I have one and none of the operating systems I tried work. George added support in trs80gp and had to patch TRSDOS 2.3 to work with it.
Also with the Kana keyboard connector CN2 is used along with CN1 to connect to the keybard which has the ROMs installed there instead of on the main board.
The standard Japanese TRS-80 Model I board is the same size as the normal TRS-80 Model I. My first thought was this might be from the TEAC PS-80, but comparing the connectors to the pictures of the PS-80 system shows a difference.
Would it be possible to get a dump of the ROMs?