Prolouge: 3 turns, because I have no idea how to do it 2 turns.
Chapter 1: 6 turns, Pretty simply, have Eirika move forward the whole time and Franz deals with reinforcements.
Chapter 2: 6 turns, Charged with Eirika and Franz, Moulder visited the village. Eirika killed the boss.
Chapter 3: 10 turns, Again, Eirika and Franz rushed forward, Neimi got Colm. Eirika killed the boss again.
Chapter 4: 9 turns, Artur was soooooooo dodgy here, and soooooooooo lucky. He dodged like 4 hits that would've killed him. Franz toke to the west south and got lute. Eirika and Lute and Franz went after the boss and Artur dodge-tanked like a boss killing all the zombie reinforcements.
Chapter 5: 11 turns, Artur is almost outta Light charges so he and Lute take the left bound track and try not to die. Franz takes the farthest west side to take out the bandits that appear and the soldiers. Vanessa visit the house. And Natasha follows right behind getting Joshua, that franz cleans everyone else up adn Eirika almost kills the boss who then dies on EM, all houses visited.
So at 5x: 42 turns