It's Ios! We haven't seen the inside of his office yet, but we did get a sneak peek of the outside on page 1 of this chapter. (It's the room jutting out.)

Ios is on the cast page, but he's not really one of the main characters. To be honest, the reason he's even on there is that there are only 4 named characters in Chapter 1, and when I first started posting the comic, I wanted to make the cast page as long as possible XD