question: We have a family friend who lives in Japan whom we have known for many years we live in the us).  When we met, he seemed like a normal person.  He has an exceptional ability with numbers (being able to mentally calculate 6~7 digit numbers in seconds) which we found amazing.  But aside from that, we have been noticing that he severely lacks social skills; as he does not seem to have any friends. To give an example, he recently contacted my brother over the phone several times and by email; when he did not receive a response, he said that he is flying over to see us.  As in other instances, he is very persistent and  refuses/cannot have anyone drift away from him.