This is a meme from "The Case Of The Portopia Serial Killer"; the original text is 'The killer is Yasu'.
...I just suddenly had one of those "Ryuukishi 07 YOU BASTAAAAAAAAAAAARD" moments you usually get while reading Umineko. Oh the drawbacks of not knowing Japanese [net]culture properly...
It's okay! Matcha got over that day, so he'll forgive me!!! He's not like he was before!!!The killer is Naz...BzzzzzzAlley-oomph!!!What do you know about Matcha!!?Uh? Was I a magic sword?Hijiriiii!!SMACKDamn, that fly can fly!!!Get a grip, Hijiri!!!And I had nothing to do with it!!!Oh, shut your trap!!!Since it is a fly.♪No, no, you don't have to write a "The butler did it" message, do you!!? This is a meme from "The Case of the Portopia Serial Killer"; the original text is "The killer is Yasu". The author is playing on the visual similarity of "Yasu" and "Naz[u]".And what's the big idea of using a gag by Midori no Matcha? A.k.a. Midori (Green Tea).