"mus_zzz_c2 - Undertale" is a high quality rip of "mus_zzz_c2" from the game Undertale.
This rip begins with gameplay footage from Undertale at the very end of the Genocide Route, then the rip turns into a YTPMV of the opening theme of the anime Shugo Chara! using the gameplay footage as the source. This is possibly a reference to (or a continuation of) the "Chara YTPMV fad" that began in early November 2015.
The rip ends with the text-to-speech voice Graham, the voice used for The Voice Inside Your Head, saying "No, I don't think so." followed by what sounds like a person being stabbed and killed, implying that The Voice has killed Chara.