Aisare Hime to Takurami no Ou Otouto Kishi - Dekiai Mitsugetsu

I'm sorry to keep you waiting, princess. I'm your knight. The Prince Knight x Innocent Princess Princess Iris was saved from the tower that she was locked in by Lilac, a knight, who became her fiancé. They went to Lucania, Lilac's country, to request permission from his parents to get married. However, Lilac's older brother, the king, compelled Iris to marry him instead. Lilac couldn't accept that, so he pressed the king for a duel. But at that very moment, Iris was accused of smuggling arms! Lilac visited her in prison. "It's time for your interrogation. Say your name." He passionately pressed her for answers even though she couldn't move! *Note: about the official English translation, this manga was combined with its prequel and is considered "The Caged Princess and Her Passing Knight Vol.2"*