For reference:
Eikichi, Mikako, Haru, Junko, Takaya, Koharu - lived on the island their whole lives
Suzuka - lived on the island as a child, moved away for 3-4 years, JUST moved back for her second year of highschool
Ryuu - visited the island as a child, moved away, came back 

For the record, I don't think it's bad if Ryuu isn't as locked in to the island as the rest of the characters. Maybe the island was a summer vacation spot for him? That would give him some background in the area, but living here would still be a new(er) experience for him.