<div class="contents">text</div>
<ul class="cp_snslink05">
<li class="cp_link facebook"><a href="#"><span>Facebook</span></a></li>
<li class="cp_link twitter"><a href="#"><span>Twitter</span></a></li>
<li class="cp_link instagram"><a href="#"><span>instagram</span></a></li>
</ul>

body {
  /*設置する親要素ページ全体ならbodyなど*/
  position: relative;
  height: 100vh;
  margin: 0;
  padding: 0;
}
.contents {
  /*サンプルはfixedの確認のためにheight指定しています。*/
  height: 2000px;
}
/*SNSリンクブロックの位置設定*/
.cp_snslink05 {
  position: absolute;
  top: 50%;
  left: 0;
  transform: translateY(-50%);
  display: inline-block;
  margin: 0;
  padding: 0;
  list-style-type: none;
}
/*それぞれのSNS iconの設定*/
.cp_snslink05 .cp_link {
  position: relative;
  width: 35px;
  height: 40px;
  color: #ffffff;
  background: #1a405f;
  cursor: pointer;
}
.cp_snslink05 .cp_link:first-of-type {
  border-radius: 0 5px 0 0;
}
.cp_snslink05 .cp_link:last-of-type {
  border-radius: 0 0 5px 0;
}
.cp_snslink05 .cp_link::before {
  position: absolute;
  content: '';
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  display: block;
  width: 1em;
  height: 1em;
  background-size: contain;
  background-repeat: no-repeat;
  color: #ffffff;
}
.cp_snslink05 .cp_link:last-of-type {
  border-bottom: none;
}
/*facebook*/
.cp_snslink05 .cp_link.facebook::before {
  background-image: url(facebook_logo_secondary.svg);
}
/*twitter*/
.cp_snslink05 .cp_link.twitter::before {
  background-image: url(x-logo.svg);
}
/*instagram*/
.cp_snslink05 .cp_link.instagram::before {
  background-image: url(instagram_glyph_white.svg);
}
/*hoverで表示されるブロックの設定*/
.cp_snslink05 .cp_link span {
  position: absolute;
  top: 5px;
  left: 45px;
  display: flex;
  align-items: center;
  width: fit-content;
  height: 30px;
  padding: 0 10px;
  opacity: 0;
  color: #ffffff;
  background: #1a405f;
  border-radius: 2px;
  transition: all 0.5s ease 0.3ms;/*hover時の動きを設定*/
}
.cp_snslink05 .cp_link:hover span {
  left: 45px;
  opacity: 1;
}
.cp_snslink05 .cp_link span::after{/*吹き出しの三角の設定*/
  position: absolute;
  content: '';
  top: 50%;
  left: -15px;
  transform: translateY(-50%);
  width: 15px;
  height: 10px;
  background: #1a405f;
  clip-path: polygon(100% 0, 50% 50%, 100% 100%);
}
/* facebook */
.cp_snslink05 .cp_link.facebook:hover {
  background: #0866ff;
}
/* twitter */
.cp_snslink05 .cp_link.twitter:hover {
  background: #000000;
}
/* instagram */
.cp_snslink05 .cp_link.instagram:hover {
  background: linear-gradient(45deg, #FF7A00 0%, #FF0169 50.06%, #D300C5 99.36%);
}