YGO TCG The Dark Magicians Sleeves (ct. 50) - Rules of Play says:
The synergy between Dark Magician and Dark Magician Girl taught us there is no bond stronger than teacher and student. Legendary Duelists: Magical Hero introduced the Fusion of Yugi’s most trusted allies, and now you can harness the ultimate Fusion of design and functionality with The Dark Magicians Card Sleeves!