This whole volume was dedicated to three teenage girls who met on a "party line" (very 90s) and formed a haphazard occult club built on their need to feel special, meant for a higher calling, since their daily lives and the people around them made them feel looked down on and unwanted. Timely topics indeed. And disturbing, although certainly plausible...self-hatred can very easily be directed outwards as a weapon.
Subaru, of course, does his best to save the girls, since that always becomes his priority...even though they've been harming other people by casting a variety of spells through phone calls, to people they've deemed "the enemy." Seishirou has a less positive view on the situation and stays close to ensure Subaru remains safe.
I'm not sure what the "bet" he refers to at the end is about - I don't think we've seen that? - but Seishirou again demonstrates a ruthlessness that's directed at everything other than Subaru. He does treat Hokuto gently, but that's likely because she's Subaru's sister, rather than a genuine connection to her as well. But perhaps he did grow to like them both.
Still not a huge amount of progress on what I'd call an overarching "plot" front, although the end of the world in 1999 deal might actually be accurate, even if the girls were inflating their own importance in it. Perhaps it's Seishirou who's the "demon" they were preparing to fight against?
I don't know when the rest of the volumes will be out, but I'll definitely be buying them as they release. And I should get started on some of those other CLAMP series while I wait.