Hangyakusha toshite Oukoku de Shokei sareta Kakure Saikyou Kishi

Synopsis

The kingdom's strongest knight, Aldia, was the central figure in ending the war between the Kingdom of Leshfeld and the Vulcan Empire. Although Aldia became a hero, he was executed as a traitor for false reasons. With regret in his heart for being unable to save the Empire's Princess Valtrune, who saved him when he was on the verge of death despite being enemies... However, when Aldia woke up, he found himself in a world six years before the war broke out! Determined to save Valtrune's life, which he could not do before, Aldia decides to pledge loyalty to the Princess as a knight of the Vulcan Empire in his second life and change the world! This is a regression story of a once-executed knight who returns to be the strongest again!! (Source: Overlap, translated)