The demon sword master of excalibur academy, vol. 2 (light novel), paperback/yu shimizu

A MYSTERIOUS HIJACK ON THE HIGH SEAS When a princess visits the Seventh Assault Garden, Leonis believes its a chance to expand his influence as a Dark Lord.

Unfortunately, the celebrations are cut short by a Void attack.

Things get only more treacherous when a rebel group seizes control of the princesss ship Leonis and the rest of his squad plan to retake the vessel, but there appears to be more at work than a simple insurrection.

And why does Regina seem to know so much about the princess?.