<!DOCTYPE html>
<meta charset="utf-8">
<style>
li { display: inline-block; }
rt { display: ruby-text; }
</style>
<body>

<div><ruby><b>firstsecond</b><li>firstsecond</li></ruby></div>
<div><rt><b>firstsecond</b><li>firstsecond</li></rt></div>

</body>