<!DOCTYPE html>
<style>
body {
-webkit-writing-mode: vertical-rl;
}
.multicol {
height: 330px;
width: 200px;
border: 3px solid #bbb;
-webkit-column-gap: 10px;
-webkit-column-count: 2;
line-height: 20px;
}
.left, .right {
padding: 5px 5px;
background-color: steelblue;
}
.float_content {
background-color: skyblue;
}
.left { float: left; }
.right { float: right; }
</style>
<div class="multicol">
First<br>
First<br>
First<br>
First<br>
<div class="left">
<span class="float_content">
left1<br>
left2<br>
left3<br>
left4<br>
left5<br>
left6<br>
left7<br>
</span>
</div>
<div class="right">
<span class="float_content">
right1<br>
right2<br>
right3<br>
right4<br>
right5<br>
right6<br>
right7<br>
</span>
</div>
First<br>
First<br>
First<br>
First<br>
First<br>
First<br>
Second<br>
Second<br>
Second<br>
Second<br>
Second<br>
Second<br>
Second<br>
Second<br>
Second<br>
Second<br>
</div>