I'm gonna hate myself for delving too deep into this, but here we go.
I don't think that the blog post and diagram are correct. Netorare is a passive stem of "netoru", the latter meaning literally "cheating" from the perspective of the homewrecker. I.e. it literally consists of the root for "sleep" merged with "steal", so — sleep (sex) stealing.
So netorare, as a word, explicitly means the state of being cheated on. Not the cheating partner, not the homewrecker, but the perceived victim. So the right arrow labeled "netorare" is incorrect, as it's derived from a passive verb form.