tokyo window fell u.s. helicopter onto school sport field near u.s. marines air base okinawa wednesday marines say late series accidents fan safety concern japan southern island japan central government okinawa authorities odds years futenma base residents complain see unfair burden carry support u.s. military presence japan 10-year-old boy suffer minor injury exact cause unclear okinawa prefecture official tell reuters boy among 50 children elementary school ground window fell u.s. ch-53e transport helicopter japan chief cabinet secretary yoshihide suga say sort incident create anxiety among involve school people okinawa never happen suga tell regular news conference government would respond appropriately get explanation u.s. officials u.s. marines okinawa say statement helicopter immediately return report incident take report extremely seriously investigate cause incident close coordination local authorities statement say regrettable incident apologize anxiety cause community say futenma base surround school hospitals shop residents worry air crash crime commit u.s. servicemen also occasionally anger residents okinawa governor takeshi onaga lead campaign get base island central government propose move less populate part island call henoko u.s. marines ch-53e helicopter make emergency land burst flame u.s. military train area northern okinawa october one injure window fall u.s. marines helicopter onto school ground japan 's okinawa