Edit in JSFiddle

$(function() {
  var controller = new ScrollMagic.Controller();
  $('.continue_img ul li').hide();

  var scene = new ScrollMagic.Scene({
    triggerElement: ".continue_img",
  })
  scene.on("enter", function (event) {
    $(".continue_img ul li").each(function(i) {
      $(this).delay(300 * i).fadeIn(1000); // 連続してフェードインさせる
    });
  })
  .addTo(controller);
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/ScrollMagic/2.0.6/ScrollMagic.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/ScrollMagic/2.0.6/plugins/debug.addIndicators.min.js"></script>

<div class="continue_img">
  <ul>
    <li>1</li>
    <li>2</li>
    <li>3</li>
    <li>4</li>
    <li>5</li>
  </ul>
</div>
.continue_img {
	ul {
		background: #fff;
		position: relative;
    text-align: center;
		li {
		  display: inline-block;
		  width: 50%;
			border: 2px solid #ddd;
			padding: 5px 0;
			margin: 20px 0 0;
      text-align: center;
		}
	}
}