Yu-Gi-Oh! Duel Monsters 5 Expert 1 is a video game for the Game Boy Advance, and the first game to follow the real OCG/TCG rules. The game is very similar to its English version (Yu-Gi-Oh! The Eternal Duelist Soul) in the story, but different in the graphics and the Booster Packs (The Eternal Duelist Soul uses the same graphic as Yu-Gi-Oh! Worldwide Edition: Stairway to the Destined Duel). Gameplay is similar to standard dueling rules, except that the Side Deck can have less than 15 cards, and is more for convenience of getting to cards for your Deck than switching between duels, as CPU duels are single duels rather than matches (though you will have a match duel against a character every two weeks on a Saturday).

Description from https://yugioh.fandom.com/wiki/Yu-Gi-Oh!_Duel_Monsters_5_Expert_1