This is not an LAC, but Stony Brook University has a fantastic Japan Center and Symphony Orchestra. My daughter was very shy, but she attended one of the largest universities for undergrad and is now in grad school at New York University. She found her friend groups not in spite of all the students, but precisely because she was at large places with so much diversity, where she could find people who shared her somewhat obscure interests. You might want to keep an open mind and look at all size universities that have strong programs that match your son’s interests.