Ah, I ended up failing to complete the full set because I was 4 cards short.. 😭😭

The 5-star yellow badge pouch isn't given out often even in events. It occasionally appears through part-timer orders, but those orders require at least 300 merge combinations. The higher the badge rarity, the more merge counts are required, making it difficult to obtain 5-star yellow or purple badges. Sigh... So close, yet so far 😭😭😭