Episode 15 of "Nanatsu no Maken ga Shihai Suru (Reign of the Seven Spellblades)" serves as the season finale and concludes the intense and emotional journey of the characters. The episode begins with the group still trapped in Ophelia Salvadori's Grand Aria, a magical world of her own making. They realize that the only way to escape is by either defeating Ophelia or breaking the spell.

Carlos, a castrato with a unique voice, appears in the Grand Aria. He sings a song that deeply moves Ophelia. Carlos confesses his love to her, and Ophelia, touched by his words, dispels the spell, allowing everyone to escape.

Back at Kimberly Academy, life returns to normal. Oliver, Nanao, and their friends resume their studies. Even Marco, the troll who befriended Katie, makes progress in his studies thanks to Katie's teaching. The characters reflect on their experiences and come to understand that the events with Ophelia were just another part of life at Kimberly Academy.

The episode ends with a sense of closure but leaves room for further adventures. The characters are shown going about their daily activities, hinting that their journey as wizards is far from over.