Crimson Spell Series by Ayano Yamane

The curse of the magical crimson sword has turned Prince Bald into a monster... To break the spell, he sets out on a journey with the sexy and gorgeous magician, Havi. Bald has no idea that when he turns into a beast at night, Havi uses his unique talents to pacify his beastly appetite... The luscious journey of Bald and Havi begins.

A curse is a difficult thing to break. Vald, prince of Alsvieth upon taking up arms to defend his country was beset with a curse that transforms him into a ravenous cannibalistic beast.

Prince Vald continues his journey with the sorcerer Halvi, seeking a means to break the curse that causes him to transform into a demon at night. But enemies looking to take the power of Vald’s cursed sword for themselves bewitch Halvi in an attempt to make him fight the young prince! Forced to the brink, Halvi makes a crucial choice.Reads R to L (Japanese Style) for mature audiences.

The key to discovering the secret behind Vald's cursed sword is somewhere in the empire of Zenedoura. With information obtained from Limris - new companion and former Consul of the Empire - Prince Vald decides to head there to see what he can find. Along the way, in order to save a gravely wounded Rulca, he deliberately chooses to turn into his demon self! Vald's uncharacteristic recklessness provokes a tirade from Halvir, who then leaves the group without a word...

On his quest to find the one behind the curse on his sword, Vald manages to sneak into the empire's capital. His target is the greatest sorcerer in Zenedoura - Asterdol. However, in the midst of his search, Vald is captured by servants of the emperor... moreOn his quest to find the one behind the curse on his sword, Vald manages to sneak into the empire's capital. His target is the greatest sorcerer in Zenedoura - Asterdol. However, in the midst of his search, Vald is captured by servants of the emperor. Fortunately for him, his capture brings an unexpected boon: the very sorcerer Vald is looking for comes straight to him! What will Vald do when he discovers that the man behind the curse looks exactly like Limris? And now that he's facing his greatest danger yet, will Halvir come to Vald's rescue? less