There's a fair argument that keeping one alive to interrogate later is the wisest move, regardless of morality on killing them or not.
But, as the MC said, keeping one of them alive. Keeping both would have been preferable since one might have information the other does not.
That's the thing I like about this particular version of the "Good Villainess vs Evil Saintess" trope: Unlike how it usually plays out, the Saintess is not naive, not an idiot, and not incompetent. She's just a bitch.
Mostly because he views Tomoe and Mio as family, like they're siblings or cousins. Unless you're a specific kind of degenerate, that isn't exactly appealing. There's also a certain amount of power dynamic: There's a level of coercion there due to the master-servant contract that he isn't...
Okay, I was worried my brain had gone smooth. So it isn't just me that couldn't understand the timeline here.
Considering she has the symbol of infinity on her, I'm going to assume:
She died at age 316, not 316 years ago. She is some kind of un-aging/cursed being.
He met her when he was 15, he...
This is probably the most nitpicky of nitpicks but...
The elf queen's face on page 19 is the worst drawn faces I've seen in a while. It's like the artist suddenly forgot how manga face proportions work.
I'm giving this series exactly one chapter after this to redeem itself. If she isn't immediately saved and/or the asshole gets stabbed in the dick, I'm dropping this series immediately.
I hate this kind of plot development.