.modal {
  display: none; /* 初期状態では非表示 */
  position: fixed;
  z-index: 1;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  overflow: auto;
  background-color: rgba(0,   
0,0,0.4);
}

.modalContent {
  background-color: #fefefe;
  margin: 15% auto;
  padding: 40px;
  border: 1px solid #888;
  width: 600px;
  text-align: center;
 
}

.modalContent__button {
    display: flex;
    justify-content: space-between;
    margin-top: 40px;
}

.modalContent__button button {
    position: relative;
    display: block;
    width: calc(50% - 20px);
    padding: 15px 27px 15px 19px;
    border: 1px solid #D8D8D8;
    border-radius: 2px;
    background-color: #FFF;
    vertical-align: middle;
    text-decoration: none;
    font-size: 130%;
    font-weight: bold;
    cursor: pointer;
}

.modalContent__button button:hover {
    opacity: .6;

}

.modalContent__button #js-agree {

    border: 2px solid #1785C4;
    background-color: #1785C4;
    color: #FFF;
}

.modalContent__button #js-agree:hover {
    background-color: #FFF;
    color: #1785C4;
    opacity: 1;
    -ms-filter: "alpha(opacity=100)";
}

.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(0, 0, 0, 0.5); /* 黒色、50%透明 */
  z-index: 0; /* モーダルより一つ下のレイヤー */
}