Hi, I resolved this problem.
By the following setting for environment variables in control pannel, Japanese characters can be saved.
Even if I don’t set this Japanese characters can be used for names of class, attribute, operation or phrase of relationship. Only the description text editor has this problem.
It seems that both saving are done by bridgepoint/src/org.xtuml.canvas.language.parent/org.xtuml.canvas.language.ui/src/org/xtuml/canvas/language/io/CanvasWriter.ja
I don’t know why only previous items work correctly.