According to Japanese site Sugoren, here are nine ways that Japanese women can instantly spot "creepy" otaku. Sugoren also collected comments and opinions from various females to draw up its list. Below are some of the women's thoughts regarding this.
1. Wearing anime t-shirts or carrying anime goods
"I imagine that his entire room is covered with cute anime stuff..." said a 20-something female.
2. Perfectly mastering dance moves otaku do at idol concerts
"While singing an idol song with friends at karaoke, this one guy broke into a perfect dance routine," said a teenage female. "It was scary."
3. Talking endless about how cute anime characters are
"The moment a guy starts talking about how cute an anime character is," said a 20-something female, "I can only think how creepy the guy is."
4. Referring to game characters as one's wife
"I recoil when I hear a guy referring to as an in-game character as 'my wife,'" said a 20-something female. "Even if the guy's cool, forget it."
5. Grinning ear-to-ear while reading a manga
"Guys that smile while reading cute sexy comics are the worst!" said a teenage female.
6. Talking like an anime character
"Not only is getting email that sounds like an anime character frightening," said a 20-something female, "I get so annoyed that I don't feel like replying."
7. Using creepy cute onomatopoeic words
"Even though this guy was a total hotty, he kept saying 'Nom Nom' while chewing his food and any passionate feelings I had vanished," said a teenage female.
8. Giving oneself an anime character name for a nickname
"This guy I was seeing wanted me to call him "Master" as if I were some maid," said a teenage female. "I was repulsed by what he was saying."
9. Only singing anime songs at karaoke
"I was worried when he was singing his heart out at karaoke in falsetto to a female anime song," said a 20-something female.
So if you are big old nerd, you might want to keep stuff like this to yourself—or, you know, find someone who accepts you for you who are. Crazy, I know!