Secret Packs are the much cost-effective and easiest way to obtain powerful yet high rarity cards in Yu-Gi-Oh! Master Duel. But in order to obtain them, they will need to unlock them first by having the keys that they have got from opening regular card packs.
Konami revealed further details regarding Yu-Gi-Oh! Master Duel. The said online card game will now have its Solo Mode added, where players will have a progression as they go on in the said mode. The developers also revealed its release date in Japan, which is in Winter of this year.