1. In Toad, select View -> Option -> Data Grids - Visual -> Fonts Grid.
2. Select "MS P Gothic", which is the Japanese Windows default, or one with Unicode in font name such as 'Arial Unicode MS'.
3. Set script to 'Japanese' in lower right corner of font dialog.
To test to see if you can see Japanese string in sqlplus:
lookup('^PAYM^10:全額振込^^1^0^|','941711');