<section class="splide" aria-label="Splideの基本的なHTML">
  <div class="splide__track">
    <ul class="splide__list">
      <li class="splide__slide">
        <button class="modal_open-button" data-micromodal-trigger="modal-1">
          <img src="https://pengi-n.co.jp/blog/wp-content/uploads/2024/01/splide-01.jpg" alt="">
        </button>
      </li>
      <li class="splide__slide">
        <img src="https://pengi-n.co.jp/blog/wp-content/uploads/2024/01/splide-02.jpg" alt="">
      </li>
      <li class="splide__slide">
        <img src="https://pengi-n.co.jp/blog/wp-content/uploads/2024/01/splide-03.jpg" alt="">
      </li>
    </ul>
  </div>
</section>

<!-- ここからモーダルエリアです。 -->
<div id="modal-1" aria-hidden="true" class="micromodal-slide modal">
  <div class="modal__overlay" tabindex="-1" data-micromodal-close>
    <div class="modal__container" role="dialog" aria-modal="true" aria-labelledby="modal-1-title">
      <header class="modal__header">
        <h2 id="modal-1-title" class="modal__title">スライダーとの併用も可能</h2>
        <button class="modal__close" aria-label="Close modal" data-micromodal-close></button>
      </header>
      <div id="modal-1-content" class="modal__content">
        使いこなせればいろいろな表現ができそうですね!
      </div>
    </div>
  </div>
</div>
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

.splide__slide img {
  width: 100%;
  height: auto;
  object-fit: cover;
}

.modal_open-button {
  width: 100%;
  padding: 0;
  margin: 0;
  background: none;
  border: 0;
  line-height: 0;
  overflow: visible;
  cursor: pointer;
}

.modal_open-button:after {
  position: absolute;
  content:"クリックするとモーダルが開きます";
  width:60%;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  padding: 2rem;
  background-color: rgba(255,255,255,0.2);
  font-size: clamp(.5rem, 2vw, 1rem);
  text-align: center;
  color:#fff;
}

.micromodal-slide[aria-hidden="false"] .modal__overlay {
  z-index: 2;
}
.micromodal-slide[aria-hidden="true"] .modal__overlay {
  z-index: 0;
}


/**************************\
  Basic Modal Styles
\**************************/

.modal {
  font-family: -apple-system,BlinkMacSystemFont,avenir next,avenir,helvetica neue,helvetica,ubuntu,roboto,noto,segoe ui,arial,sans-serif;
}

.modal__overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0,0,0,0.6);
  display: flex;
  justify-content: center;
  align-items: center;
}

.modal__container {
  background-color: #fff;
  padding: 30px;
  max-width: 500px;
  max-height: 100vh;
  border-radius: 4px;
  overflow-y: auto;
  box-sizing: border-box;
}

@media screen and (max-width: 480px) { 
.modal__container {
  max-height: 90vh;
  max-width: 300px;
}
}

.modal__header {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.modal__title {
  margin-top: 0;
  margin-bottom: 0;
  font-weight: 600;
  font-size: 1.25rem;
  line-height: 1.25;
  color: #00449e;
  box-sizing: border-box;
}

.modal__close {
  background: transparent;
  border: 0;
}

.modal__header .modal__close:before { content: "\2715"; }

.modal__content {
  margin-top: 2rem;
  margin-bottom: 2rem;
  line-height: 1.5;
  color: rgba(0,0,0,.8);
}

.modal__btn {
  font-size: .875rem;
  padding-left: 1rem;
  padding-right: 1rem;
  padding-top: .5rem;
  padding-bottom: .5rem;
  background-color: #e6e6e6;
  color: rgba(0,0,0,.8);
  border-radius: .25rem;
  border-style: none;
  border-width: 0;
  cursor: pointer;
  -webkit-appearance: button;
  text-transform: none;
  overflow: visible;
  line-height: 1.15;
  margin: 0;
  will-change: transform;
  -moz-osx-font-smoothing: grayscale;
  -webkit-backface-visibility: hidden;
  backface-visibility: hidden;
  -webkit-transform: translateZ(0);
  transform: translateZ(0);
  transition: -webkit-transform .25s ease-out;
  transition: transform .25s ease-out;
  transition: transform .25s ease-out,-webkit-transform .25s ease-out;
}

.modal__btn:focus, .modal__btn:hover {
  -webkit-transform: scale(1.05);
  transform: scale(1.05);
}

.modal__btn-primary {
  background-color: #00449e;
  color: #fff;
}



/**************************\
  Demo Animation Style
\**************************/
@keyframes mmfadeIn {
    from { opacity: 0; }
      to { opacity: 1; }
}

@keyframes mmfadeOut {
    from { opacity: 1; }
      to { opacity: 0; }
}

@keyframes mmslideIn {
  from { transform: translateY(15%); }
    to { transform: translateY(0); }
}

@keyframes mmslideOut {
    from { transform: translateY(0); }
    to { transform: translateY(-10%); }
}

.micromodal-slide {
  display: none;
}

.micromodal-slide.is-open {
  display: block;
}

.micromodal-slide[aria-hidden="false"] .modal__overlay {
  animation: mmfadeIn .3s cubic-bezier(0.0, 0.0, 0.2, 1);
}

.micromodal-slide[aria-hidden="false"] .modal__container {
  animation: mmslideIn .3s cubic-bezier(0, 0, .2, 1);
}

.micromodal-slide[aria-hidden="true"] .modal__overlay {
  animation: mmfadeOut .3s cubic-bezier(0.0, 0.0, 0.2, 1);
}

.micromodal-slide[aria-hidden="true"] .modal__container {
  animation: mmslideOut .3s cubic-bezier(0, 0, .2, 1);
}

.micromodal-slide .modal__container,
.micromodal-slide .modal__overlay {
  will-change: transform;
}
// splide
const options = {
  cover: true,
  heightRatio: 0.5
};
const splide = new Splide(".splide", options);
splide.mount();

// Micromodal.js
MicroModal.init({ awaitCloseAnimation: true, awaitOpenAnimation: true });

External CSS

  1. https://cdn.jsdelivr.net/npm/@splidejs/splide@4.0.7/dist/css/splide.min.css

External JavaScript

  1. https://cdn.jsdelivr.net/npm/@splidejs/splide@4.0.7/dist/js/splide.min.js
  2. https://unpkg.com/micromodal/dist/micromodal.min.js