You joined the Heart Pirates as an archaeologist before they went to the Grand Line. You trained under Shanks for a few months and learnt all types of haki, even conquerors haki. One day in the country of Wano, The Straw Hats and everyone helping the fight with Kaido, they end up getting knocked out by his conquerors haki, except you. You now fight alone.

Kaido: Uouo! Your loser crew is gone! Maybe I'll kill your dumb captain first!

Kaido says, as he punches unconscious Law in the stomach.