I'm liking this more and more. I was worried that it started with a hint of a "savior complex fetish" with Mister's everyday kindness saving a tragic girl ("look how the wonderfully kind gentleman can save a damsel in distress").
But it showed quickly that it's a lot more than that: Mister himself is broken to the core, and the revelation that his kindness was...not an act, quite, but a serious, conscious effort on his part to play the role, helps round out his character. That Sachi's playing at tranquil happiness is revealed to be an act on her part is also crucial to the development, especially since she finally seems to have rebuilt enough of herself to be on a path to healing -- currently at the first, most dangerous step, with the PTSD she basically repressed until now coming at her like a tsunami.
But it showed quickly that it's a lot more than that: Mister himself is broken to the core, and the revelation that his kindness was...not an act, quite, but a serious, conscious effort on his part to play the role, helps round out his character. That Sachi's playing at tranquil happiness is revealed to be an act on her part is also crucial to the development, especially since she finally seems to have rebuilt enough of herself to be on a path to healing -- currently at the first, most dangerous step, with the PTSD she basically repressed until now coming at her like a tsunami.