Even before Yamaoka and Kurita were drafted into the Ultimate Menu project in the first chapter, Kurita had daily tasks to do, even as a new employee (and Yamaoka was surely as well, though we don't see it since he's a lazy oaf).
This way, it's safe to say that they both still have other tasks to do (both on- and off-screen) outside the project — the project surely can't be their only work, after all.