Seriously? I might order a T-shirt with Rachel and Renka pics on it. By the way, I've noticed you around these forums for a year or so. Your English does seem to have improved noticeably since then. *shrugs*. That was rather random, I know.
*gives a happy cookie and a apology for not understand the joke*
He's referring to the greatest anime ever, "Sayanora Zetsubo Sensei", starring a hero literally named "Mr. Despair". The guy goes all emo and says "Zetsuboshita" (translates to "I am in despair" ) at every opportunity he can get. Kina is just linking up the despair reference from this Bleach chapter to that.