imgnum=1;
function changeImage(){
    if(imgnum==1){
        document.koma.src="http://www.chou2.jp/contents/manga/img/004/2.jpg";
        imgnum=2;
    }else if(imgnum==2){
        document.koma.src="http://www.chou2.jp/contents/manga/img/004/3.jpg";
        imgnum=3;
    }else if(imgnum==3){
        document.koma.src="http://www.chou2.jp/contents/manga/img/004/4.jpg";
        imgnum=4;
    }else if(imgnum==4){
        document.koma.src="http://www.chou2.jp/contents/manga/img/004/1.jpg";
        imgnum=1;
    }
}


imgnum=1;
function changeImage1(){
    if(imgnum==1){
        document.back1.src="img/001/2.jpg";
        imgnum=2;
    }else if(imgnum==2){
        document.back1.src="img/001/3.jpg";
        imgnum=3;
    }else if(imgnum==3){
        document.back1.src="img/001/4.jpg";
        imgnum=4;
    }else if(imgnum==4){
        document.back1.src="img/001/1.jpg";
        imgnum=1;
    }
}


imgnum=1;
function changeImage2(){
    if(imgnum==1){
        document.back2.src="img/002/2.jpg";
        imgnum=2;
    }else if(imgnum==2){
        document.back2.src="img/002/3.jpg";
        imgnum=3;
    }else if(imgnum==3){
        document.back2.src="img/002/4.jpg";
        imgnum=4;
    }else if(imgnum==4){
        document.back2.src="img/002/1.jpg";
        imgnum=1;
    }
}


imgnum=1;
function changeImage3(){
    if(imgnum==1){
        document.back3.src="img/003/2.jpg";
        imgnum=2;
    }else if(imgnum==2){
        document.back3.src="img/003/3.jpg";
        imgnum=3;
    }else if(imgnum==3){
        document.back3.src="img/003/4.jpg";
        imgnum=4;
    }else if(imgnum==4){
        document.back3.src="img/003/1.jpg";
        imgnum=1;
    }
}


imgnum=1;
function changeImage4(){
    if(imgnum==1){
        document.back4.src="img/004/2.jpg";
        imgnum=2;
    }else if(imgnum==2){
        document.back4.src="img/004/3.jpg";
        imgnum=3;
    }else if(imgnum==3){
        document.back4.src="img/004/4.jpg";
        imgnum=4;
    }else if(imgnum==4){
        document.back4.src="img/004/1.jpg";
        imgnum=1;
    }
}