there is thin red line between genius and insanity, and this show is crossing the line twice, and then starts to jump the rope using the line, all the while singing happily :P
stop this train, erm, anime i’m getting out! /sarcasm off :P
Anyway, we now have no less than 3 groups vying for the diary: Himari and her bros, Masako and her brother, and finally Ringo (and her deceased sister?) while the pink haired bishonen with his black rabbit flunkies seems to manipulate at least 2 of the factions. We can as well enjoy the insanity while it provides us fanservice.
my conjecture is that tabuki is the ringmaster of the “fabulous max” faction, acting as the intelligence gathering while Yuri is only acting as the decoy/fall-man. Since it has been hinted several time that he knows what truly happened to momoko by alluding to her as schrodinger cat.