Two meanings of the name
“Blackjack” can mean the card game also known as 21, or the manga created by Osamu Tezuka and starring Dr. Black Jack. Because both are associated with the same name, context distinguishes the casino game from the medical-fiction series.
In the card game, each player tries to reach a total of 21 without going over and plays against the dealer. The classic version described in the supplied rules uses six decks, and a natural blackjack—a two-card hand—pays 3:2. The dealer stands on 17, including soft 17, a hand with an ace counted as 11 without busting.
How the game works, and the manga’s details
Each player and the dealer receive two cards. Players’ cards are face up; the dealer shows one card and keeps the other face down. A player can then hit, stand, double the bet for exactly one more card, or split a pair into separate hands. In the described version, players may split into as many as four hands and double on any two cards; surrender is not available. The stated house edge is 0.43% with basic strategy, but that figure applies to this particular set of rules.
If the reference is Tezuka’s work, Black Jack is a manga in the drama, suspense, and medical genres, published by Akita Shoten in Weekly Shōnen Champion. It ran from September 19, 1973, to October 14, 1983, and was collected in 25 volumes. Its central character is a doctor called Dr. Black Jack. References to cards, a dealer, or bets point to the game; references to Tezuka, the doctor, or the manga identify the fictional work.