Who sings the ending song from da anime k-on?

[Kriss1]

whats her name? http://www.youtube.com/watch?v=IsEBTPDKaXw

 

[KnowledgeIsBliss]

"Don't say 'lazy'" by Aki Toyosaki, Yoko Hisaka, Satomi Satou and Minako Kotobuki

 

[mandy]

Hikasa Youko (Mio's voice actress), does the main vocals.