Sora wa Akai Kawa no Hotori: Shokan

To commemorate Sho-Comi's 50th anniversary, this one-shot story—Chie Shinohara's first appearance in the magazine in 16 years—unfolds an alternate story leading into the fifth paperback volume. It depicts an episode from the journey of Prince Zannanza, brother of Prince Kail, as he travels to marry the Egyptian queen.
(Source: Comic Natalie, translated)