A Cold Timbre...! The Black Princess Appears! - S1.E13

Haruka becomes interested in the violin after coming across a mysterious masked girl and coming to admire her violin playing. Minami takes Haruka to meet her violin instructor, who gives her a violin of her own, which was the first one he ever made. After struggling to play under Miss Shamour's instruction, Haruka once again comes across the masked violinist, who teaches her how to play. The next day however, Haruka and the others discover the masked violinist is actually Dyspear's daughter, Princess Twilight, who uses her own Dark Dress-Up Key to power up Shut, who in turn target's Minami's instructor to create a powered-up Violin Zetsuborg. Despite their opponent being stronger than usual, the Cures manage to defeat the Zetsuborg, after which Haruka manages to play the violin from her own heart.