.tab-container {
  display: flex;
  flex-wrap: wrap;
  margin:10px 0;
}
.tab-container:after {
  content: '';
  width: 100%;
  height: 3px;
  background: #1875a4;
  display: block;
  order: -1;
}
.tab-item {
  color: #1875a4;
  background: #eee;
  line-height: normal;
  font-weight: bold;
  font-size: 16px;
  text-align: center;
  padding: 15px .5em;
  order: -1;
  position: relative;
  z-index: 1;
  cursor: pointer;
  border-radius: 5px 5px 0 0;
  flex: 1;
}
.tab-item:not(:last-of-type) {
  margin-right: 5px;
}
.tab-content-box {
  width: 100%;
  height: 0;
  overflow: hidden;
  opacity: 0;
}
/* アクティブなタブ */
.tab-switch:checked+.tab-item {
  background: #1875a4;
  color: white;
}
.tab-switch:checked+.tab-item+.tab-content-box {
  height: auto;
  overflow: auto;
  padding: 15px;
  opacity: 1;
  transition: .5s opacity;
  border: 1px solid #1875a4;
}
/* ラジオボタン非表示 */
.tab-switch {
  display: none;
}