Ayame looks like a pressure cooker about to explode that can only release some steam in her "special" time before sleep. It starts to build up again as soon as she's with the other 3.
Kagari is steadily building pressure also, and they reinforce each other without realizing it.
Sango seems mostly oblivious, while Shinobu is on alert because she feels something is happening.
There's no lovey dovey, "you are my fated person", feelings involved here. Just raw teenage horniness, like just about any teenager. And that makes it realistic.
It's really fun to read. I hope the following chapter gets published soon.