Verdant Lord

In the near future, nature strikes back against humanity as vegetation overruns cities and wooden, mech-like creatures called Arethusa attack. The story begins while the apocalypse is unfolding, rather than after it has passed. Souma Shin, a punk kid from Japan, visits his twin brother Ken. When an Arethusa invades the compound, Shin discovers a group of young children being used for military purposes and tries to save them amid the chaos.