Don't think there's any Yui here, to be honest. The sleepy one (second up to down from the right side) is Ritsu, she's actually quoting a line from the anime.

Well, not quoting verbatim, but making a reference to a quote from the anime.

Mugi must be p.o.'d for being depicted as a fish (and possible lunch).

MezzoDragon said:
Mugi must be p.o.'d for being depicted as a fish (and possible lunch).

'Fish'

Lol, she just likes fish.