No idea how Kaiba got to know the exact location of Yugi and his friends, but whatever. Yugi returns his deck, that he retrieved from the first player killer, and Jonouchi challenges Kaiba to a duel, as a revenge for what he put them though at the Death T arc. Anyway Kaiba agrees if only to test out his new duel disk system, which also has different rules compared to the regular game system. Makes sense, and ofc this was never explained in the anime cause why should they bother, haha.