The A6M5 mod. 52 Otsu, designated as the Type 0 Carrier-based Fighter Model 52B (零式艦上戦闘機五二型乙), is the second minor modification of the A6M5. The Model 52B (Otsu) retains the belt-fed 20 mm Type 99 mod.2 mark 4 from the Model 52A (Kō) with 125 rounds per gun rather than 100, but comes with an additional 13.2 mm Type 3 machine gun in exchange for a single 7.7 mm machine gun. Other additions to the Model 52B include 45 mm thick armoured glass to the windscreen, a larger propeller spinner, and a revised gas outlet near the windscreen.

It was introduced in Update 1.37. With all the modifications done to the A6M5 over the other A6Ms, performance has improved but it faces stronger enemy aircraft which proportionally perform even better. While still unrivalled in manoeuvre dogfights capable of dodging, weaving, and out-turning the pursuer into getting on their six, staying on the six of an aircraft will be harder to maintain due to the higher top speeds all other aircraft will have over the A6M5. The A6M5 otsu's 13.2 mm HMG gives the plane an additional tool to fight with, gaining additional damage output when using all guns, and still posing a threat if the 20 mm cannons run out. As last the main-production A6Ms, the A6M5s in War Thunder also come with a late-war modification which allows them to be converted into "bakusen", mounting a 250 kg bomb in place of the centreline drop tank.