As someone fragile of health and struggling with clinical depression, this series struck a bit too close to home for comfort.... and made my day just that lil' bit brighter.
Rest in peace, Kotoha-Sensei.
It's hinted that Tsukasa lived through much of Japan's history and remembers a good deal of it, so something like Touhou that makes fun of history might be too cringy for her taste.
From a DnD player's point of view, he's the type of munchkin minmaxer that will ruin every game and make them borderline unplayable for everyone involved... but this is exactly the point: he's not trying to have fun - he's here to make sure the "game" is as unplayable as possible for whoever...
I'm seriously wondering if the MC was a military member (most likely JGSDF due to this is a Japanese work) or so in his past life... Full-auto AR-15, pump-action shotty, glock pistol, mines, dedicated kill-zones... Just who was him before he became a demon lord? That said, what is that poison...