yo so

theory:
Takiishi and Umemiya aren't fighting
because he's also from the orphanage and him hitting people " standing in his way " is because he's in survival mode? the sensei from their orphanage comes and they have a moment?

or Takiishi only knows fighting, doesn't care about anything else
he is stronger than Ume and therefore the strongest but he just doesn't care to leave behind a legend etc but since Ume seems to only use fighting as a tool to achieve his goal and getting stronger seems secondary, Takiishi will obliterate him to the point Ume won't be able to fight anymore -> Sakura won't have to fight him to take over as leader
speaking of, they're on a roof, Takiishi has the opportunity to do the funniest thing.... throw Ume off the familar roof (get it? because of his backstory)

Either way, I need Sakura to simply still be the only one standing at the end of the mentioned time limit in the war declaration
and Endo just gets picked up by his boyfriend because he's gotten bored of it and they walk off together lol