"Dark Blastoise" is a card that appeared in the early days of the Pokémon Trading Card Game (the era of the old back design) and remains extremely popular among collectors today. The reason for its popularity is not just nostalgia, but also its rarity, unique backstory, and design. The appeal of the "Dark" series: The card's original backstory—that Blastoise was "modified and controlled by Team Rocket and became aggressive"—which is not present in the original games, made a strong impact on children at the time. Illustration by Mitsuhiro Arita: Created by the renowned illustrator Mitsuhiro Arita, who has been active since the first generation, the heavy and powerful artwork stimulates a desire to own it. Highly valuable "old back design": Included in the fourth expansion pack, "Team Rocket," released in 1997, this card is over 25 years old, and its value has skyrocketed due to the scarcity of cards in mint condition.