Complex sentence: A Shimagaijin (島外人) is a person who is not of Ryukyuan descent but lives in Okinawa Japan because he/she prefers to and who also has adjusted to the ways of the Okinawan people and lifestyle.
Split into simpler sentences: A Shimagaijin (島外人) is a person who is not of Ryukyuan descent but lives in Okinawa Japan because he/she prefers to. Also has adjusted to the ways of the Okinawan people and lifestyle.