Earlier this years I was able to visit where Fort Shokoji was located at during the Battle of Okehazama. Highly possible that Nobunaga constructed the fort in 1559, one year before the battle. The fort was located south of Odaka Castle. According to Sieshiro Mizuno's book, Okehazama he no Michi, Sassa Masatsugu was supposed to be in charge of the fort. There is still no absolute answer on that.