Timeline — Shinobi Era (SE), Year 1 = Konoha's founding:
SE 1–29: Era of peace under Hashirama's leadership as 1st Hokage — roughly 29 years of growth and stability following the village's founding.
SE 29: Hashirama dies. Murakami, age 8, attends the funeral/memorial.
SE 29–30: The peace holds for only a few months after his death before old tensions resurface. Tobirama (2nd Hokage) is already leading by this point; he dies at some point to the Silver and Gold brothers, elevating Hiruzen to 3rd Hokage — I've placed this during the early-to-mid war years so it doesn't disrupt anything already established.
1st Shinobi World War: SE 30–37 (7 years). Starts essentially on the heels of Hashirama's death — thematically, his death is what destabilizes the peace he built.
SE 37: War ends, armistice signed, 20-year non-aggression treaty begins. This is the story's present.
Murakami: born SE 22, age 8 at Hashirama's funeral (SE 29), currently 15 (SE 37) — 7 years elapsed, matching the war's full span.