Even in Samurai Warriors they make Kojiro into a villainous type for barely any reason. They always portray him as some pale faced snake man when he was just a guy doing his job and was even civil and courteous to Musashi prior to the famous Ganryujima duel.

Instead Musashi shows up, screams abuse at Kojiro after being told he was late for the duel, openly disrespects him, grabs the oar and whacks him over the head with it.

Then he has the fucking balls to say in his memoirs when he was an old man "Sasaki was the greatest swordsman i ever fought!" that one guy you insulted and cruelly murdered.