Hikigaya and Oreki himself was not really a patriotic person when the Fall happens.
Both of them were high school students and their biggest worry was about the college admission or what to eat in the lunch cafeteria, whether they could have a fulfilling life in schools and the angst of teenage boys before the Fall
Then the Fall happens, and they were thrust into a position of great power.
They become a warlord, and a leader and these two after battling each other countless of time become comrade and allies and then as natural as the water flowing, the people of Japan themselves nominate them as the Two Sage Guardian of Japan
Not once during those times, they show any desire to restore the Japanese monarchy or to create a new Japan.
Instead, if one looked at their actions at that time, they were more like separatist warlords intending to become the most powerful on the land
They were high school students, so they did not know how to use legitimacy of cause to their advantage.
