<!DOCTYPE html>
<style>
    body {
        -webkit-writing-mode: vertical-lr;
    }
    .multicol {
        height: 330px;
        width: 200px;
        border: 3px solid #bbb;
        line-height: 20px;
    }
    .left, .right {
        padding: 5px 5px;
        background-color: steelblue;
    }
    .float_content {
        background-color: skyblue;
    }
    .left { float: left; }
    .right { float: right; }
    .column1, .column2 {
        float: left;
        height: 160px;
    }
    .column1 {
        margin-bottom: 10px;
    }
    .column1 > .left, .column1 > .right {
        width: 110px;
    }
    .column2 > .left, .column2 > .right {
        padding-left: 0;
    }
</style>
<div class="multicol">
    <div class="column1">
        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>
            </span>
        </div>
        <div class="right">
            <span class="float_content">
                right1<br>
                right2<br>
                right3<br>
                right4<br>
                right5<br>
            </span>
        </div>
        First<br>
        First<br>
        First<br>
        First<br>
        First<br>
        First<br>
    </div>
    <div class="column2">
        <div class="left">
            <span class="float_content">
                left6<br>
                left7<br>
            </span>
        </div>
        <div class="right">
            <span class="float_content">
                right6<br>
                right7<br>
            </span>
        </div>
        Second<br>
        Second<br>
        Second<br>
        Second<br>
        Second<br>
        Second<br>
        Second<br>
        Second<br>
        Second<br>
        Second<br>
    </div>
</div>