JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrapper">
    <div class="wrapper-inner">
    <div class="item">
        <div class="viewer">One</div>
    </div>
    <div class="item">
        <div class="viewer">Two</div>
    </div>
    <div class="item">
        <div class="viewer">Three</div>
    </div>
    <div class="item">
        <div class="viewer">Four</div>
    </div>
    <div class="item">
        <div class="viewer">Five</div>
    </div>
    <div class="item">
        <div class="viewer">Six</div>
    </div>
   </div>
</div>

CSS

.wrapper {
    position: relative;
    width: 400px;
}
.wrapper-inner {
    height: 180px;
    overflow-x: hidden;
    overflow-y: auto;
    background-color: red;
}
.viewer {
    display: none;
    position: absolute;
    right: 0;
    top: 0;
    bottom: 0;
    left: 200px;
    background-color: orange;
}
.item {
    width: 200px;
    height: 60px;
    background-color: green;
    cursor: pointer;
    outline: 1px solid black;
}
.item:hover {
    background-color: cornflowerblue;
}
.item:hover .viewer {
    display: block;
}