A group of four kids wake up in silent world covered in ash that seemed completely devoid of colour and living things. At least that's how it seemed but then they noticed that the gigantic sky piercing tree-like pillars in the distance were in fact moving. They were moving slowly and they were moving towards them. Not wanting to see what might happen to them if they stayed put, the kids make their trek away.
Hours pass. Despite their best efforts, one of the eldtrich structures was nearly upon them. That's when the ground in front of it erupted into a grey storm of ash and earth as a gargantuan turtle-esque monster tackles the thing. The pillar begins to fall over from its clash with the beast and a man in a large hood approaches them from where the earth opened up. He quickly ushers them behind an upended chunk of rock and tells them to brace themselves for the incoming shockwave that's about to hit them.
The children wake up once again to the hooded man making a strange ethereal emerald bonfire. He greets them in a cheery fashion and tells them he's glad they're here. He explains that they're in the far, far future and that he's been trying for a long time to bring them here. The world is now overrun with by unearthly beings and the event that brought those things into it takes place in their time. He tells them there's nothing that can be done about them now in his time but they can do something about it in theirs.
The giant turtle they saw earlier is one of the seven great beasts linked to the event and the man is its bonded master. One of the seven was the trigger to this future so he needs them to hunt down where they slept and narrow down which one to destroy. To achieve that end, he will teach them the arcane arts and have them periodically travel back to the future to ensure they pull it off.
He sends them back one by one until it's just one boy left with him. Instead of sending him back right away, he takes off his hood and reveals who he is - the boy's future self. He reveals that the rest of the kids will become bound to the their respective beasts as well and he warns his younger self that one of them is going to be the one who causes all this. The real plan is to have his younger self awaken and bond with his beast faster than the rest and destroy the others in their weakened states before the end of the humanity can begin.
Yes and their future versions as well since pretty much only those bonded with the beasts could survive and remain somewhat human. They all had a falling out over the apocalypse but a lot of time passed and they just kinda tolerate each other as they wander the world finding things to do.
Not much to say about plot except the kids try to stop the apocalypse and that future MC is true final boss after they prevent the original event. Also, it gets revealed that an eighth beast existed but only woke in the future world and that's what MC forces a bond with after he gets NTR'd.
- Future MC connected the two times together via arcane magic but the past doesn't change anything in the future. They're separate timelines but the future does still have clues about the past. Ash comes from the pillars and preserves things well.
- They use effigies to displace things in time temporarily but the more powerful something is, the greater the cost. It's why future MC doesn't just go back in time at first since he needs to make sure his beasts on both ends are ready to permanently transfer him. He also set up a lot of effigies to build up energy over the years to carry out his plan.
- Bonding with the beasts slowly corrupts their humanity and they're more eldritch than human in the future.
- Some of the beasts can reproduce and have offsprings/offshoots that are repopulating the world.
- Future MC and his beast kinda share the same mind but still separate enough to love each other as individuals. He did it all literally just to shrink her down to his size and give her a younger monster girl form.
- Magical energy is plentiful in the future but sparse in the past so beasts and magic are small scale in the past. It's the pillars that generate all the energy in the future.
- The pillars are people fused together through forced instrumentality and seek out new humans to take in and they're just a byproduct of one of the beasts reproduction method.
I had this quite a bit more fleshed out than how I described it. The kids would come to and from the present and future to see what changes have taken effect and they'd travel to see all their future selves to figure out the truth of the end. The world's end would be inevitable because all the beasts would cause the apocalypse in their own unique fashions depending on which awakened completely the quickest and ends with MC sacrificing himself to drag his future self back to his time crippled since he sacrificed his own beast's body to send himself into the past. The kids would never find out that they need to kill all the beasts to truly save the world but by then their bonds with their beasts compel them to protect their own no matter what. I'd want at least 1 kaiju battle to happen in the climax of this story.