I think that you all should note this: Neru and Haku have made appearances at Nico Nico Party 2013 in the following songs:
If You Do Do/Pomp and Circumstance by Miku, Luka, Gumi, Mayu, IA and Rin
Life Reset Button by Gumi
Cheat Life Game by Gumi
And last but not least
The Earth's Final Confession by Gumi
Hope that can by added :)