The actual visual novel explains things much better. I haven't played it, but i've read about it. I'll just put this spoiler, since it'll be long. [spoiler]Tomoya had (unknowingly) been collecting those light orbs by getting to know all the different people during the course of the story. All the girls, Sunohara and Mei, the dorm mother, that other girl involved with the gangs or whatever, and his father. At the end of each characters story, an orb is obtained. In the VN, you have to gather all the light orbs to complete the Nagisa AfterStory route. It's rather hard to translate that well into an anime form where only one girl is the "true" path. For the Other World part, that's a little more complicated. I understood it as a place Ushio created after she died. (how can she do that? Who knows. It's not really explained.) It's implied that Tomoya collapses and dies alongside Ushio. After he dies, he goes the Other World, inside the little doll. After the whole sequences in the other world, Tomoya is set back in time by Ushio (the girl in the other world) to the point where he first met Nagisa. Thus, the whole sequence about whether or not he wants to get to know her again, since he knows what happened in the first timeline. Now, in this second timeline, Tomoya has a bunch of light orbs that he collected from the first timeline. Then, as Nagisa is dying, he is able to make a wish for Nagisa to live. The anime really doesn't explain any of it well, which is shame.[/spoiler]

Well it definitely has something to do with the "older" Ushio and "robot version" of Tomoyo, and that orb that grants any wish...I think that had something to do with it too. I dunno about that second part though. But I accept your challenge and here's what I think happened. Ok so Ushio (the older one) said that if she died, then the Illusionary World would not exist anymore. So with her death, obviously, the Illusionary World ended, along with all of those light orbs. So if the Illusionary World and those light orbs "ended" when Ushio died, then that means that when she was born, the Illusionary World was created and the light orbs went there. So with her death, I think time reverted itself back to when she (Ushio) was born. That's my take on it, no idea whether it's what really happened or not, but I gave it a shot.