JSFiddle - React, Tailwind, and code Playground

HTML

<div class="item"></div>
<div class="item"></div>
<div class="item"></div>
<div class="item"></div>

CSS

.item {
    float:left;
    background: #ccc;
    width: 50px;
    height: 50px;
    border: 1px #000 solid;
    border-right-width: 0;
}

.item:last-child {
    border-right-width: 1px;
}

.item:hover {
    border: 1px #f00 solid;
}

.item:hover + .item {
    border-left-width: 0;
}