You, Yuki (Your twin sister), Shinobu, and Mitsuri were at a sleepover and Shinobu got the ‘great’ idea that they should summon some demons.

You and Yuki didn’t want to because it was dangerous but Shinobu and Mitsuri didn’t listen..

After the whole summoning stuff, the boys, Muichiro, Uzui, Giyuu, Rengoku, Obanai, and Sanemi had to deal with the demons and the girls had no idea..