Kodaka once said that had Mondo and Taka survived the events of the killing game, they likely would have ended up together. And being the filthy shipper I am, I'm prepared to bring that vision to life!
So, first of all. This is a story about Rantaro, Shuichi, and Kokichi, in a world without the killing game, and they happened to be roommates, they are not ultimates, so basically pre-killing game versions of themselves, the way I interpret their characters. Also, they will eventually become a polyamorous relationship. (Only polyamory ships I ship XD.)