Shimousa (as well as Shinjuku) establish really quickly that Guda has an… interesting, sense of danger. They probably won’t charge headfirst if they know for a fact they’ll die (see: when monk bro slaughter an entire village, though I can’t remember if Musashi had to hold back Guda or not) but it’s established time again that they’re a reckless bitch. Staying too close to battle because that’s where they’re the most useful. Barely caring as they roll all the way down the hill. They’ve become pretty desensitized to danger, just like them two kids, something about which Musashi outright says “yeah I’m not really sure that’s a good thing?”
But I mean, who cares, right? You’re a badass! You killed Tiamat! This is, like, your tenth singularity fixed (eleventh if you’re one of the poor suckers who played Agartha) You fistfought Solomon! Guda slaps, and you, the player, slaps.
And then there’s That One Scene.
Shimousa is quite singular among singularities for many reasons, but the most important of them is that you’re basically alone. Sure, Musashi is here, Muramasa is here, Kotarou is here, but that’s it. Mash isn’t with you. Chaldea isn’t with you. Your servants aren’t with you. And that makes you weaker. The Shimousa duels are hard as balls because you are, story-wise, relying mostly on Musashi. But where Shimousa really hammers home that you are alone, that you’ve never gotten anything done alone, that your strength was always in bonding with others, is during That One Scene.
Alone, you are weak. Alone, you are powerless. Alone, you would die.
Your strength was never in raw power.