The Minogame's Protection legendary amulet in Assassin's Creed Shadows increases damage for empty Armor slots, so Yasuke is better off naked.

Once you take control of Yasuke for the main game, you’ll find a whole new arsenal of abilities to destroy your foes with

Having the ability to not only block, but Parry red attacks as Yasuke is a game-changer for combat. This makes the Protector's Armor the best early-game armor for Yasuke. There is really no need to find another Legendary Chest Armor piece until much later in the game.