Ahhh, what beautiful art! And it's even animated with Live2D!
The facial expressions have quite a few variations, which is great.
Spoiler
Mary is crazier than expected, but the story works so well because Hazel is just as calm and vigilant.
It might be a different meaning than "toxic yuri," but in Japan there's a term called "crazy psycho lesbian." For some reason, that term came to mind.