The first issue of what happened between the X-Men and the Inhumans in the eight months after Secret Wars is out, and we get parallel stories of the X-Men in Muir Island and the Inhumans in Matsumoto.

First, the X-Men.
spoilers:
Scott's team responds to the distress call from Madrox, and when they enter the facilities, the Mist (as yet not identified by them) starts to affect Scott. Seeing the first dead mutant, they then find the Madrox duplicates dead outdoors, with the original Madrox revealing them that it was Terrigen Mist before he also dies. Scott and Emma contact Beast and update him whereupon he replies that he will do his own research on it. Scott collapses but later makes it out with Emma. And, he blames the entire Inhuman race for releasing the Mist and declares war on them.
end of spoilers

Next, the Inhumans.
spoilers:
As the Inhumans marvel at the lack of panic in Matsumoto. As the Mist rolls, cocoons start to emerge when a HYDRA squad shows up to secure them and kill the crowd. Whereupon Crystal warns them to leave or she will use lethal force and a fight breaks out. As she and Flint combine their powers to take out HYDRA she is knocked unconscious and the team is trapped inside Flint's stone shield which HYDRA then heats up. Before they burn up, a newly emerged NuHuman spontaneously uses his power, which entrances most of the HYDRA agents motionless. Crystal then dispatches them. The NuHuman says it worked well ("うまくいった.") and Crystal greets him ("はじめまして, 私 は クリスタル." "Nice to meet you, I am Crystal.") He says he is Daisuke, and he speaks English, adding that he is glad he no longer feels alone. Crystals invites him to join them if he wishes.
end of spoilers

In the end,spoilers:
both Scott and Crystal say, "We protect our own."
end of spoilers