21 out! Or how to "play it smoothly". X)
I like how all the couples in this series seem to have a "hot" one (Ayaka, Moe, Izumi, Yukina, Sawa) and a "cool" one (Yurine, Mizuki, Chiharu, Towako, Itsuki), yet they all play this dynamic in their own specific way.
Though I'm starting to wonder if the hot one isn't actually Itsuki in this case…
Regarding the "disappearance"… Itsuki's theory is probably not far off. Yurine could have said "hey, let's skip together, it'll feel like we're eloping!"