The Type 4 (Mod 4) Karo-Tei was an experimental anti-submarine patrol airboat built for the Imperial Japanese Army (IJA) by Yokohama during the late stages of World War II. Modified from the Type 4 Karo-Tei boat, it featured a pair of Nakajima Kotubuki 41 engines derived from the Ki-27 fighter at the stern instead of a petrol engine-powered propeller. Not much is known about this variant’s operational history other than that it did not survive the war.

Introduced in Update 1.91 "Night Vision", the Type 4 (mod. 4) is a direct upgrade over its tech tree counterpart, the Type 4 (mod. 2), thanks to its unique airboat configuration; while the engines are exposed to enemy fire, they also allow the boat to accelerate and decelerate very quickly, as well as doubling the top speed over the base variant. Its armament consists of a single 37 mm gun at the bow and a pair of 20 mm guns amidships. Due to the 37 mm gun’s relative inaccuracy and lack of damage output, the 20 mm is generally more reliable against most targets. However, the Mod 4 retains its shallow draught from its tech tree counterpart, resulting in very poor stability in rough seas. In addition, the boat's hull is very fragile and can be easily damaged.