TL:DR, Week 1
Sun starts becoming a black hole. There was an hour warning before the end of the world, which ended up being quite a few due to impossibily difficult calculations involved in destruction and warping of celestial bodies. Some attempt to flee Poqmori on spacecraft, but are sucked into the singularity. Eventually, the planet is absorbed too.
Folks wake up on a new world. They still have carried and nearby belongings. Electronic technology fails. Some become delusional from shock, some go outright crazy, others manage to keep their wits.
Scouting by flight begins. People end up gathering by the river, where the opposite side of the singularity can be seen as a dark spot in the water. Celebi and Arceus arrive and explain the situation, along with the fact that some people among the group have become divine.
Godform transformations begin, assised by Celebi. Ciere becomes a Mewtwo. Rachel becomes a Ho-oh. Atria becomes a Deoxys.
Samantha the Renamon, now a god, tries to murder Lepus the Lopunny. The attack is stopped in a joint effort by Ciere, Vanilla the Blaziken, and Lepus himself. Lepus attempts peaceful negotiations with Samantha that fail, and Samantha is preemptively killed by Atria and Rachel in order to prevent further trouble.
Samantha's death annihilates a one mile radius, the blast impacting up to a ten mile radius. Mortals are protected by the gods, but the landscape is scarred. Samantha's ship, the Phoenix, self-destructs and rains metal ore across the landscape. The blast area is repaired in a joint effort by Rachel, and Vanilla (who just prior had changed into a Dialga).
A lone Vulpix, Blaze, wanders into a rift created by the destruction of Samantha, entering the Spirit World. The resulting actions mutate the Vulpix line into a Fire/Ghost type, and add a final evolution called Kitsune after Ninetales.
The night falls. Some depart, some settle down by the river.