About the Ruka's illusion part :
Actually is not so crazy to think Ruka could be the one who created the illusion of Kaname killing Aido - dono .
I had read from some posters before that have doubts if Kaname killed Aido - dono or it was only a trick .
Now is confirmed at chapter 81 that part of Ruka's power is to create elaborated illusions . That are supposed to be believed by almost anybody .
There was this part of Ruka and Kain not being so affected as expected for the death of their favorite uncle . Only worried about Hanabusa well-being ( and also not as worried as expected ) .
Kaname appears to desire keeping Yuuki , Hanabusa and Kaien Cross from messing with his plans . Or to any of them passing to his side . Because Kaname is worried about the safety of the people who believe most in him . ( The exception here is Ruka . Kaname couldn't make her change her mind in any way possible . )
Kaname needed an easy way to escape .
And the most important reason of all : Kaname wants to be seen as the greatest villain in existance . That his actions are the ones of a madman ( his words , not mine ) . He is planning to become a scapegoat . Kill all purebloods , them let Yuuki kill him . Letting Yuuki as the only survivor .
It 's now not impossible to think Kaname and Ruka planned to make Cross , Hanabusa and Yuuki believe they see Kaname killing Aido - dono .
Why any of the present didn't notice it was an illusion is not so difficult to explain . Hanabusa was in shock to see his beloved father killed . He would believed anything he saw at that time . Yuuki ran as quick as she could after Kaname . Cross notice and left after Yuuki a few seconds after . So both Yuuki and Cross left the place in a rush . No one of them could had stay long enough to notice anything wrong from the scene . Also non - purebloods vampires only turn into dust . The evidence could be lost after they leave . There is a strong possibility than nobody of the presents returned to Hanadagi's Castle to look for the dust remaings of Aido - dono .
Nor anybody who cared to be a detective and made an DNA test on those samples .No witness to check if the kill was faked or not .
I did hope the killing of Aido - dono was only a trick used for Kaname to make his loved ones desist of following him . Because this is the only crime so far that has no good explanation yet . And it's very difficult to save Kaname if he indeed had killed an innocent .