I’m pretty sure Viz had a translation error regarding Kaiba mentioning how many duels he had with Yami Yugi. He said “this is our third duel together”. Just to clarify to people who may have been confused, Kaiba and Yami actually had 4 duels together, not 3.
1. In volume 2 when Kaiba stole Grandpa’s Blue Eyes White Dragon card and thus Yami Yugi pursued a monster card game to obtain the card back, that then introduced Kaiba’s penalty game that lead to Kaiba’s trauma and inventing Death-T.
2. Volume 5, Death-T where Kaiba and Yugi dueled in the simulation box.
3. Duelist Kingdom when Kaiba was forced to duel against Yami Yugi in order to rescue Mokuba from Pegasus.
4. Their current duel here in the Semi Finals from Battle City.