I got a nice 33% raise last year ( my salary wasn't that high ).
Since then, I've taken up very important responsibilities for the company, and basically am no longer a dev.

 - I founded a branch office in a foreign country. 
 - Found the proper place for the office. 
 - Hire people.
 - Coach them. 
 - Set up the workspaces.
 - I am Scrum Master in one project, about to become in a couple more.
 - I run the payroll, calculate invoices, meet legal obligations and whatnot...

Basically running this place.  All of that applies only to the branch office.

How can I justify a 25% raise? I don't want my boss to think I'm being unreasonable, in case that I am.

This is a bit unique from the other raise questions here because I received such a large raise last year too.