I'm on chapter 27 and I have a prediction based on what we've seen so far.
The commander was probably the previous master of the demon sword and had some sort of relationship or feelings for MC in the first life. He probably also killed everyone he cared about, including her. Somehow he managed to replace the demon sword with the holy sword, but then his love interest ended up the new host. Not sure by whose design. So he probably remembers all 3 lives at this point and that's why he doesn't hold any animosity toward her for being unable to resist the sword.
At any rate, it's interesting enough. I have good expectations as long as the author can keep up what they've done so far.
