OVA
Description
Karen, Princess of the Kasen Kingdom within the Renza Federation, stands third in the royal line of succession as the eldest child of the crown prince's eldest child. Her true name is Lady Shien Rengoku Kasen. Alongside partners Hakuren, Gyokuren, and Suiren, she ultimately becomes one of Seina Yamada's wives.

As part of a covert mission, Karen and her companions serve as ladies-in-waiting to Lady Seto. Their initial objective is stealing advanced technological secrets, potentially a Juraian Royal Treeship, to combat piracy plaguing their home territory. This operation proceeds without Seto's explicit authorization but aligns with her broader strategies, as Seto likely identified their identities early through her intelligence.

Personality-wise, Karen exhibits practicality and modesty compared to her peers. Described as the youngest in her group, she displays tomboyish traits rooted in childhood dreams of piloting mecha. Her combat proficiency compensates for her lower bio-enhancement level (level 5), achieved through rigorous training. Initially lacking domestic skills like cooking due to her royal upbringing, she develops a genuine enjoyment for these tasks under Seto's tutelage, where culinary skills are mandatory for attendants.

Karen's narrative involvement intensifies upon meeting Seina Yamada. In the novels, this occurs earlier than in the anime, with her group assigned to escort Seina to Mikagami after he aids Seto's pirate-gathering operations. She subsequently acts as his covert bodyguard at Galaxy Academy, serves aboard his ships, and works as a maid at Amane's residence with her companions. A significant bonding moment occurs when Karen visits Seina's Earth home and discovers Japanese anime and tokusatsu featuring giant robots. Sharing Seina's passion for mecha, she connects with him over this mutual interest, as Seina explains piloting such robots is a common boyhood dream.

A pivotal event unfolds during Seina's wedding to Kiriko, Amane, Ryoko, and Neju. Karen and her partners reveal their true identities and kidnap Seina, fleeing towards the Renza Federation. The anime portrays a scandalous escape: discarding clothing and ship components to outrun pursuers, then broadcasting themselves molesting Seina to assembled dignitaries as "proof" of elopement. The novels depict a more conventional abduction. Their destination is Racepshi, a planet-sized entertainment starship facilitating their jump from Galactic to Renza territory, with Kiriko's group narrowly boarding before the jump. This neutral location allows both factions to operate without allegiance conflicts or Galactic Federation policy violations.

Post-abduction, Karen's group undertakes limited anti-piracy operations with Seina and his mecha Zinv. These missions prove fruitless, as royal forces repeatedly intercept them, claiming targeted pirates as their own prey. After Seina disappears during a confrontation with HIMC, necessitating a random jump to an unknown location, Karen collaborates with Kiriko's team on dual objectives: continuing pirate suppression and searching for Seina. Future timelines confirm their eventual reunion and joint combat.

Politically, Karen's father, King Kasem, proposes Seina as a potential successor to the Kasen throne. Following unresolved events in the Renza Federation, Karen and her partners return to Earth married to Seina—a union strengthening ties between Renza, Jurai, and the Galaxy Federation. During Earth visits, Karen frequently represents her group in diplomatic meetings.

Additional traits include possessing minor wound-healing properties in her saliva, which inadvertently causes misunderstandings when observed. Her uniform features red sleeves matching Amane's GP uniform in the anime, though this color-coding lacks narrative significance in the novels.