This looks like Len on Len, as in twincest rather than incest as the tags suggest..

The pixiv title says it's Len on Len.
In fact, it looks like Len x Len is a pretty popular theme on pixiv.

Is it twincest or dual_persona though?

Oh yeah, dual persona it would be.

act.1 x act.2

Huh, I didn't know there was a selfcest tag.