During the Fourth Shinobi World War, Iō was assigned to the Logistic Support and medical Division. During a quell in the war, with heavy casualties coming into the compound, the KIA scroll was stolen Sukui assigned Iō along with Yokaze, Sakura Haruno, and Yūgao Uzuki to retrieve it as it contained the corpses of shinobi with kekkei genkai and other unique abilities sealed away in it. When the team caught up to the opposition, Iō fought alongside his comrades and was successful in sealing away both the Suna, and Kumo-nin. However, his confrontation with Hayate Gekkō ended with him being heavily wounded. Healed by Sakura, Iō was not able to continue on the mission and left the sealing of Hayate to his remaining comrades. Their mission ended in success with all three shinobi being sealed away successfully.