What happens:
Unity.exe won't start. You'll see nothing but black window.

How to reproduce:
Install Unity at the path including multi-byte character.

It happens any Windows, I tested Windows10(64bit). Mac was OK.
I tried several versions,
Unity 5.1*
Unity 5.2*
Unity 5.3*
all of them causes this issue.
Unity 4.6.9 won't start as well, but it shows
Error loading page
Problem with the SSL CA cert (path? access rights?)

Please use below letters for the example of multi-byte character,
全角テスト
this means the "multi-byte character test".