Top-Tier Diner of the Apocalypse

Ryan runs a System issued food truck in the middle of a zombie apocalypse. His cooking restores one hour of humanity to any undead who eats it, and the System rewards him with memory crystals ranging from D to S grade. This week's target: a single S grade crystal within seven days. Such a crystal can only form inside an undead who has managed to stay intact, hunting its way back toward someone it once loved.