<div class="cp_box1">
  <input id="cp01" type="checkbox">
  <label for="cp01"></label>
  <div class="cp_container">
    <h1>タイトル</h1>
    <p>テキスト</p>
  </div>
</div>

.cp_box1 {
  position: relative;
}
.cp_box1 input {
  display: none;
}
/*開くためのボタンとテキストを隠すグラデーションの設定*/
.cp_box1 label {
  position: absolute;
  display: flex;
  flex-direction: column;
  align-items: center;
  z-index: 1;
  bottom: -10px;
  width: 100%;
  height: 140px; /* グラデーションの高さ */
  cursor: pointer;
  text-align: center;
  /* 以下グラデーションは背景を自身のサイトに合わせて設定してください */
  background: linear-gradient(to bottom, rgba(250, 252, 252, 0) 0%, rgba(250, 252, 252, 0.95) 90%);
}
/* 開いた時にグラデーションを消す */
.cp_box1 input:checked + label {
  background: inherit;
}
.cp_box1 input:checked + label {
  /* display: none ; 閉じるボタンを消す場合コメントアウトを外す */
}
.cp_box1 .cp_container {
  overflow: hidden;
  height: 250px; /* 開く前に見えている部分の高さ */
  transition: all 0.5s;
}
/*続きをよむボタン*/
.cp_box1 label:after,
.cp_box1 label::before {
  content: '';
  position: absolute;
  line-height: 2.5rem;
}
.cp_box1 label:after {
  z-index: 2;
  bottom: 20px;
  width: 13em;
  content: '続きをよむ';
  color: #ffffff;
  background: #1b2538;
  border-radius: 20px;
}
.cp_box1 label::before {
  position: absolute;
  bottom: 38px;
  left: calc(50% - 3.5em);
  z-index: 3;
  width: 10px;
  height: 5px;
  background: #ffffff;
  clip-path: polygon(50% 100%, 0 0, 100% 0)
}
/*閉じるボタン*/
.cp_box1 input:checked + label:after {
  content: '閉じる';
}
.cp_box1 input:checked + label:before {
  left: calc(50% - 2.5em);
  transform: scale(1, -1);
}
.cp_box1 input:checked ~ .cp_container {
  height: auto;
  padding-bottom: 80px; /* 閉じるボタンのbottomからの位置 */
  transition: all 0.5s;
}

<div class="cp_box2">
  <p>表示しておくテキスト</p>
  <input id="cp02" type="checkbox">
  <label for="cp02">続きを読む</label>
  <div class="cp_container2">
    <p>続きを読むで出てくるテキスト</p>
  </div>
</div>

.cp_box2 {
  width: auto;
  margin: 30px auto;
}
.cp_box2 input {
  display: none;
}
/*続きを読むボタン*/
.cp_box2 label {
  font-weight: bold;
  position: relative;
  display: flex;
  flex-direction: column;
  justify-content: center;
  width: 80%;
  margin: auto;
  padding: 0.3em 1em;
  cursor: pointer;
  transition: all 0.3s;
  text-align: center;
  color: #da3c41;
  border: 2px solid #da3c41;
  border-radius: 3px;
}
/*＋マーク*/
.cp_box2 label::after {
  position: absolute;
  content: '';
  right: 16px;
  width: 16px;
  height: 16px;
  background: #da3c41;
  clip-path: polygon(0 40%, 40% 40%, 40% 0, 60% 0, 60% 40%, 100% 40%, 100% 60%, 60% 60%, 60% 100%, 40% 100%, 40% 60%, 0 60%);
}
.cp_box2 label:hover::after {
  color: #ffffff;
}
/*hover*/
.cp_box2 label:hover {
  transition: all 0.3s;
  color: #ffffff;
  background: rgba(218, 60, 65 ,0.7);
}
.cp_box2 label:hover::after {
  background: #ffffff;
}
/*-マーク*/
.cp_box2 input:checked ~ label::after {
  background: #da3c41;
  clip-path: polygon(0 40%, 100% 40%, 100% 60%, 0 60%);
}
/*hover*/
.cp_box2 input:checked ~ label:hover::after {
  background: #ffffff;
}
.cp_box2 div.cp_container2 {
  position: relative;
  z-index: 10;
  overflow: hidden;
  height: 0;
  margin-top: -1px;
}
.cp_box2 input:checked ~ div.cp_container2 {
  transition: height 0.5s ease-in-out;
}
/* 高さを設定 */
.cp_box2 input:checked ~ div.cp_container2 {
  height: auto;
}