the TV tropes description of the guy
Complete Monster: Lord Naritsugu is The Caligula to an insane degree. His very first scene has him raping the daughter-in-law of a lord who’s hosting him for the night, and then killing her husband for good measure. This isn’t an isolated incident, either. Naritsugu has been doing this for so long, he threatens the very stability of the nation, and nobody can touch him as he’s the Shogun’s brother. Later, we see him tie up a family for target practice (including a little girl) and hear how he massacred a peasant revolt, taking the leader’s daughter, after cutting out her tongue and chopping off her limbs, for his use as a sex slave. His only reaction to seeing the titular assassins mow down his loyal soldiers who die in defense of him is to contemplate how amazing the era of war must have been while deciding to return to such days.