Nice story. There's a chance that any of them or even all of the women(leaning toward the latter) participate in the 'correspondence'. But even if it is just one of them, by Wakui spending time with all three of the women, it obscures which one is the one that's "Yukari".... and yet has the same effect even if its all of them. That's nice writing =03.
Thanks a lot for the translation \(^,^ )!