As you may know, Japan is brought up on manga and anime and even as adults, citizens enjoy these two mediums which are seen as being childish by some societies outside of Japan.
I find it unfortunate that folks feel pressure to give up what they still love from their childhood. A BBC reporter asked me if I felt childish liking anime culture and owning figures - I replied by asking him whether he owned Star Wars toys. He replied that he stopped when he reached the age of 12 as that stuff "was for kids."