Can simply be another world or a POSSIBLE future (or past, since Jamie's arc already ended), or even the PAST ITSELF (yea, before the goddesses went crazy. Nobody said this CJ is really the MC, right?).
I don't think the dev would put Jamie/Tsukiko as a villain
I did not know that you were suppose to start over to see the prologue for chapter 40. ..
I think your theory is wrong. Watching that prologue it's a flashback memory of himself when he was not former shards of himself.
1. The 4 rings are not of Victoria and the girls because it's the original bond rings of the 4 season deities that followed him when he was the original Lord
2. He knows not of Cro at the time he has this past lives recollection that came from Chad Thundercock
3. It appears his 4 followers were captured or trapped somehow so he entered the void that ripped him into shards when he went to rescue the 4
4. The 4 eventually started to search for their Lord but found that he was ripped into thousands of pieces of himself (shards)
5. For who knows how long each of these shards they found were not their Lord so each came up with their own twisted way to save their Lord. This conflict on how to save their Lord caused them to destroy many worlds.
This is why their is no ring for Jaime as this is the original Lord. This is also why he has Mizue shotgun as it's the original weapon of her after all the girls are shards/incarnations of the original 4 deities and contain some of the power of one of the original 4. Also we know how Cro was able to retain more of her sanity as she was also bonded to all 4 also she had the exact same rings as his original self.