var intro_on=new Image();
intro_on.src="./img/top_navi_intro_a.gif";
var intro_off=new Image();
intro_off.src="./img/top_navi_intro.gif";

var story_on=new Image();
story_on.src="./img/top_navi_story_a.gif";
var story_off=new Image();
story_off.src="./img/top_navi_story.gif";

var cast_on=new Image();
cast_on.src="./img/top_navi_cast_a.gif";
var cast_off=new Image();
cast_off.src="./img/top_navi_cast.gif";

var system_on=new Image();
system_on.src="./img/top_navi_system_a.gif";
var system_off=new Image();
system_off.src="./img/top_navi_system.gif";