Thank you very much for your reply.
1. Other applications allow me to save with multi-byte code strings (in my case, in japanese). I had never tried to save a file with multi-byte code strings, but I just confirmed it with notepad, paint, and OOo.
2. I don't know if any specific character causes a problem because, you know, there are thousands of characters in japanese and I don't have energy and time for that. But it seems that it always happens when the file name contains any multi-byte code (at least, japanese). Because I tried with couple different characters for "Auto-save" but any of them didn't work and it happened with all the scenario (which means (sort of) many combination of different characters) I played in japanese so far.
Btw, Wesnoth does not accept japanese input in the save file dialog and filter option for the load game dialog (none of the characters were shown in the box).
3. OK, here is a bit tricky part. I edited wesnoth.po and wesnoth-tsg.po to remove the entries for saving file and the scenario name. There are 4 of them in wesnoth.po, Auto-save, Turn, Replay, and another replay. First, I deleted all of these four and 1st and 2nd scenario names in TSG. The result was good. The program made auto-save files and did not freeze at the end of scenario.
Then, I played TB from the beginning, whose scenario names are in japanese. Then, as I expected, auto-saves was not made and the game did not respond at the end of scenario. I looked at the file name in the manual save and replay save option. The part of file name, which corresponds to the scenario name was in japanese. OK. I knew that, so it's fine.
But when I loaded a saved scenario from TB, it made a auto-save file successfully. I looked at the file name in the manual save and replay save option and I found the scenario name was in English. I continued to play to the end and press "End Scenario" button. Then, the program was hanged up. This is probably because the next scenario name is in japanese (the current one is too, though) therefore the program tried to save with it.
So, I tried to examine with only one entry is translated for each 4 of them, and tested with 4 cases, TSG (senario names are in english) new game and loaded game, and TB (scenario names are in japanese) in both.
Results were pretty much straightforward. When "Auto-save" is translated, none of them could make a auto-save file. TSG could advance to the next scenario but TB couldn't (btw, TB cannot proceed to the next scenario in any case).
The auto-save file does not contains a term "Turn", so with translated "Turn", there is no problem in auto-saving except TB new game, because it contains scenario name in japanese. And no problem in advancing to the next scenario for TSG. Of course, in the case of manual saving, you have to remove "*turn*" to make a save file because it's in it.
There are 2 entries for "replay"; one, henceforth r1, which is reference to savegame 841 seems to be the entry for auto-saved replay at the end of scenario and the other, r2, savegame 140 and 142 is for manually saved replay file. So, when r1 is translated, it gives me an error message after pressing "End Scenario" button but can go to the next scenario (only for TSG). With translated r2, there is no problem except there is multi-byte code in replay file when trying to save it manually and you have to remove it to save.
OK, that's what I found today. The temporal solution (removing the entries for auto-save, turn(not so important one though), replay, and scenario names) certainly avoids the problem. But It leaves the scenario names in English, therefore not perfect. And why does the loaded game gives english file name even though the scenario name is in japanese and only for that scenario?