In Astah Professional and Astah SysML, you can change the font of model elements in the [Font Chooser] dialog. There are two ways to open the [Font Chooser] dialog.
Font setting dialog in Astah
A) From Property View
Right-click the root package in the structure tree and then select [Set Font]
B) From Property View
Select the root package in the structure tree and then go to its Property view (The bottom left pane) and then click the Default Font button.
When the Font chooser box first opens, all of the top check boxes are ticked with the default setting. Uncheck them in order to choose your preferred font style. Also checking [All Available Font Families] box will show all the font styles that you can select.
If you are using the free edition, download free trial of Astah Professional to try it out.
Cheers,
SJ
Astah in 5min 
Is there a way to change the font of a single element in a diagram?
Not in the current version but will be available in the next release in Sep!
How to change main language from Japanese to English. I had choice English at install process, but running by Japanese. I do not how to change it. Pls
Hi Santin, thanks for getting back to me.
Q1: Which edition are you using, Astah Professional or Community?
Q2: Which OS are you running Astah on?
Thanks,
Satomi
I using Astah Professional on Win 7. System Language is Japanese, but I want use English for Astah. PLs help me. Thanks.
Hi Santn,
Follow this step below.
1. Close Astah if you have it running
2. Open “astah-pro.l4j” file with a text editor which you can find in Astah Installation folder
3. In the file you will find a line “#-Duser.language=en”, remove the # and overwrite this file
4. Restart Astah – should launch in English
Thank Satomi. I has changed success.
My pleasure, Santn!