so.. ive stumbled upon a manga called green worldz. Read a couple of chapter and seem really interesting.
Resemble alot shingeki no kyogin, basically nature flip out and earth suddenly get invaded by giant (and pissed off) flowers, insect and plant/human hybrids that wage war and feed over japanese ppl (think its worldwide tho, also doesnt seem alien invasion). survivors of the first attack, sort of manage toget their stuff togheter (barely) and look for others... (main char has its own purposed etc blabla). Very rough, same as shingeki.
Ill keep reading it, i dont dig nature/insect idea, but story overall seem good so far.