From our internal Support Site: "There does not seem to be an out-of-the-box solution for altering the default font of Tahoma that is used by ArcGIS Pro. There does not seem to be any environment settings to control this that can be altered within the interface of Pro, similar to the ArcMap Options. However, the non-Latin characters should be able to display switching to an appropriate font. For example Meiryo font for Japanese characters. NIM099934 seems to indicate that font fallback will be implemented in Pro in future releases. "