If any single individual or company was responsible for the art style that makes Japanese manga and anime so instantly recognizable for what it is, who/what is it?

by COCK_FRIDGE

What was the genesis of this culturally ubiquitous character design?

andromedakun

I think you should look into the life of Osamu Tezuka.

He was one of the first to create an animation studio (mushi productions) and to use the wide eye style that is so much in use today.