The forth and fifth seasons are titled Grunge and Shoegaze to continue the rock genre theming of the two previous seasons. Grunge also refers to grim, punk, and vileness, which plays with the Darker and Edgier story taking place in a crime-ridden garbage town. Shoegaze being named after a variant of alternative rock also fits with it being a direct sequel to Alternative.
Medical Mechanica's Executive Director Yamaguchi tells exploits of his childhood which Shin didn't buy. But following the revelation that Orinoko's father transferred his dying wife's mind into a robot body, it could mean Yamaguchi was a human himself. But that revelation then dives into Nightmare Fuel territory since Haruko uploaded a virus into him through a sushi-like flash drive, essentially killing him in the worst possible fashion.
