If you have a custom stage, then you can do that (and if not then copy stage.hscript), and here's how.
Put these before "function start(song)"
var sh_r = 1; var movex = 0; var movey = 0; var xup = true; var yup = true; var movexby = 0.025; var moveyby = 0.005;
Put these in "function update(elapsed)"
var sh_toy = -2480 * movey * sh_r * 0.45;
var sh_tox = -330 * movex * sh_r;
dad.x += (sh_tox - dad.x) / 12;
dad.y += (sh_toy - dad.y) / 12;
movex += movexby;
movey += moveyby;
if (movex >= 2){
movexby = -0.025;
}
if (movex <= -2){
movexby = 0.025;
}
if (movey >= 0.25){
moveyby = -0.005;
}
if (movey <= -0.25){
moveyby = 0.005;
}
You should have the enemy moving around, sorta like how it works in God eater.