Gensaku Saikyou no Last Boss ga Shujinkou no Nakama ni Nattara?

A man is reborn as Euglam, the Empire's most powerful third prince and final boss from the fantasy novel *The Sacred Hero Iris*, which was later adapted into a game. To prevent his fate of being killed by Iris, the protagonist and princess of the opposing kingdom, he seeks refuge in her realm. Expecting a comfortable life, he instead finds himself training Iris in swordsmanship, serving as her bodyguard, and engaging in personal relationships, including a close bond with a young assassin. His Magic Core allows him to create impenetrable magical barriers, making him nearly untouchable. As he navigates this new role, a story unfolds between the powerful former antagonist and the seemingly innocent yet possibly violent protagonist.