That whole deal about growing up and behaving like an adult? Scrap it, you don't have to — at least not in the Japan of recent years. Adult responsibilities, adult worries, adult concerns — while we all know such things exist, it's become possible to dodge them well into your 30s and 40s, in a kind of sedated state of child-nirvana.
Japanese culture — especially after the nation's surrender in World War II, has nurtured a child-fixation that deems childhood as the ideal state of being. Perhaps the hardships of war, the humiliation of defeat and subsequent dramatic collapse of prewar values — sacrificing your life for the common good and prosperity of the family and nation — prompted people to seek a psychological escape hatch.
In any event, while prewar Japanese media paid hardly any attention to children, the postwar media came to be overrn by okosama bunka (kiddie culture), manga and anime being the prime examples.