Because he is a Denpa-Human and fuck rules he can be invisible/intangible whenever the fuck he wants because he's a fucking Denpa-Human and nobody should be able to see him. The only reason he's solid is either because of the intense power of the Andromeda Key, or if you go by anime-canon, he can shift between real and Wave World at will. IT DOESN'T MATTER. it's the first reason btw
no subject
it's the first reason btwhow did you guess