Even if we assume the most likely point about Sousuke, that he's the one that's engaged to Hiro, it still doesn't begin to explain why he's absent or what Daddy Mind Games is trying to accomplish with all of this.
After previously planting that photo of Sousuke, did he even plant that game save to make them think Sousuke had been there? If so, why? Did he actually arrange the baby switch? What's the point of any of it?
All we know so far is that he's A. extremely wealthy, B. quite guarded about his motivations, and C. a skilled and experienced manipulator. We know just enough to be suspicious of everything connected to him but not enough to understand anything about either his goals or how much he's willing to screw with people to achieve those goals.
That aura of mysteriousness might be intriguing at first, but it can quickly become frustrating when the audiences feels like they aren't getting any closer to understanding The Truth of the story. I don't want to be frustrated with this series, as I'm become fond of all four main characters, but I really hope we start getting some inkling soon of what's really happening.