How A Realist Hero Rebuilt The Kingdom Vol. 5 (Light Novel)

In Vol. 5, a new nation, the Kingdom of Friedonia, is born, and Kazuya becomes the new king. While he steadily works toward enlightening the kingdom’s people through broadcasting his educational program, he visits the floating city of Lagoon City, which is ruled by Excel, who has been appointed Supreme Commander of the National Defense Force. Awaiting him there is Castor, the former General of the Air Force who Kazuya previously defeated. When Castor becomes suspicious of Kazuya’s sudden visit, he reveals the National Defense Force's top secret project! What orders will Kazuya give Castor, who has been dumbstruck by the unimaginable sight he witnesses?
Notice: This book is written in Japanese.