Yep, it’s going exactly as I was hoping.
At a first glance, it looks like this manga is aware of the problems with having two partners, and is using that to create comedy. Sort of like how DomeKano knows incest is complicated and uses that to develop drama.
Saki is appropriately nervous, Naoya is surprisingly reasonable, and Nagisa is convincingly naive, and nobody so far is unlikable. As long as these characters can have each other’s best interests in mind, I think I can enjoy this. And who knows? Maybe they can actually make this insanity work.