Glitch: Sometimes when Yuna's friend is sleeping over the effect she is supposed to give just doesnt appear. The sleep meter still goes up quickly even when theres a sleepover, the only time the effect was active was during the after party.
Hi,
That's not a glitch, kaede being in Yuna's room isn't a trigger for any "special" effect, she's just there for you to play with, the only special effect, as you said is night just after the party, when both Yuna and kaede had one too many beers and they are quite tipsy, which in turn makes the wakefulness meter fill much slower.
Cheers