Ryota Hori 
Record of Wortenia War (Manga) Volume 5 [EPUB ebook] 

After Ryoma’s inspired use of thaumaturgy to wash away the enemy, all eyes are on him. Along with Helena Steiner, he stands poised to win Rhoadseria’s civil war for Princess Lupis!

But as the war approaches its climax with the battle of Heraklion, the enemy uses schemes and trickery to change the rules of the game. In the midst of betrayal, Ryoma finds his greatest chance yet to suppress the civil war!