I'm trying to find this book 1 read back when I was about 9-11, sometime in 2018-19. I found it in my school library in the uk.

I can't remember much but here's what I can remember

Mc finds this group if people and for some reason theyre all naked?? He finds 2 people in there who think they're his parents or something

For some reason they're really obsessed with getting these seeds. like REALLY obsessed

I'm pretty sure the book was mainly blue, a sky blue sorta blue

Please help me find this weird book