Question: How long is the island where one school of the Kyūshū Collegiate American Football Association is located?

Context paragraphs:
Kyūshū Collegiate American Football Association: The Kyūshū Collegiate American Football Association (九州学生アメリカンフットボール連盟) is an American college football league made up of colleges and universities primarily on the island of Kyushu, Japan; one school is located on Okinawa Island.

Kyushu Palookas football: The Kyushu Palookas football program represents the Kyushu University in college football.  They are members of the Kyūshū Collegiate American Football Association.

Ryukyus Stingrays football: The Ryukyus Stingrays football program represents University of the Ryukyus in college football.  Ryukyus is a member of the Kyūshū Collegiate American Football Association.

British Universities American Football League: The British Universities American Football League (BUAFL), is an American football league contested by university teams in the United Kingdom as part of the British Universities and Colleges Sport (BUCS) organisation.  The league was formed by the British American Football Association (BAFA), the national governing body of American football in the UK, in 2007 as the successor to the British Collegiate American Football League, after BAFA withdrew its recognition of the British Student American Football Association which ran that league.  The BUAFL has been credited with reviving interest in American Football in the UK.

2015 Heiwadai Bowl: The 2015 Heiwadai Bowl is a college football bowl game that was played on Sunday, November 1, 2015 at Heiwadai Athletics Stadium in Japan.  Seinan Gakuin University representing the Kyūshū Collegiate American Football Association and Hiroshima University representing the Chushikoku Collegiate American Football Association.  Seinan Gakuin beat Hiroshima by a score of 17-7.

UTEF Lions football: The FUTE Lions football program represents the University of Teacher Education Fukuoka in college football.  FUTE is a member of the Kyūshū Collegiate American Football Association.

Seinan Gakuin Green Dolphins football: The Seinan Gakuin Green Dolphins football program represents Seinan Gakuin University in college football.  Seinan is a member of the Kyūshū Collegiate American Football Association.

Okinawa Island: Okinawa Island (沖縄本島 , Okinawa-hontō ) is the largest of the Okinawa Islands and the Ryukyu ("Nansei") Islands of Japan.  The island is approximately 70 miles long and an average 7 miles wide, and has an area of 1,206.98 km2 .  It is roughly 640 km south of the rest of Japan, roughly the same distance off the coast of China, and 500 km north of Taiwan.  The Greater Naha area, home to the prefectural seat of Okinawa Prefecture on the southwestern part of Okinawa Island, has roughly 800,000 of the island's 1.3 million residents, while the city itself is home to about 320,000.

Heiwadai Bowl: The Heiwadai Bowl (平和台ボウル) is an annual college football bowl game played in Japan between the champions of the Kyūshū Collegiate American Football Association and the Chushikoku Collegiate American Football Association.  The winner of the Heiwadai Bowl advances in the West Japan postseason, with a chance to play in the Koshien Bowl.  The game is regulated by the Japan American Football Association.

Tokyo Bowl: The Tokyo Bowl is an annual American college football bowl game, usually played in December in Tokyo, Japan.  The game matches up the 2nd place team from the Kansai Collegiate American Football League and the 2nd place team from the Kantoh Collegiate American Football Association.

Supporting paragraphs: Kyūshū Collegiate American Football Association Okinawa Island
Answer: approximately 70 miles long