Anime and manga, while a popular medium enjoyed by many and well-known for its pop culture presence in Japan, may not be as popular as one might think. "Otaku culture" is more often referred to as an obsession from the get-go.
This is how Japanese society works best kept a secret, since passions can have a negative impact on a person's reputation. After all, anime is not real and surely collecting figurines and cosplaying is not normal? If the majority are not otaku, then it's assumed that no one else is. That's why being an otaku would not cause you much shame.
The Geeky Friend
The geek was the main protagonist in earlier West films; they were the ones who fueled the jokes and the second favorite to the main character in the film. This may apply to real life, where anime was out of the norm until it reached the mainstream. Or having to watch their favorite anime's next episode on Toonami every Saturday night was another story.
Enter an American exchange student who will study in Osaka. She is an avid collector, artist, cosplayer, and gamer. On her purse and backpack, she has many buttons of Menhera-chan and other adorable keychains she's acquired over the years at various cosplay conventions. She's never berated for it, and stays treated the same as the other returning visitors to Japan. Surely Tokyo doesn't represent Japan as a whole.
Where Are The Waifus?
Osaka is much more laid back and friendly, and locals are a lot more open and helpful. Just like in Tokyo, they warmly welcome the outsider to Japan and wish her well, using tatemae mannerisms as appropriate. For the most part, the way of living and physical environment is consistent to anime and manga, but one day she spots another girl with an anime pin on her bag, making any "otaku" proudly confesses that she is an otaku.
When she visits another otaku in Sannomiya, they both openly admit they're otaku. After all, being an otaku is best kept a secret! Having multiple groups of friends isn't a social issue, although they won't be recognized as "truly" Japanese.
Unfortunately, an "otaku" foreigner will not always have a good time as this one did - especially among the older generation, in professional settings, and in smaller areas - but to see the separate lives that Japanese otaku lead offers a different perspective of living in Japan as a full-time resident. This is not a bad thing, though, and everything is best enjoyed in moderation.