In a crossover fanfiction, perhaps the Hollows in Bleach start causing chaos in the Dragon Ball Z universe. The Z - fighters are confused by these strange spiritual entities. Ichigo arrives to help deal with the Hollows. He teaches the Z - fighters about the nature of souls and how to detect and fight Hollows. In return, Goku shows Ichigo new ways to increase his power level. They form an alliance and together they train to become even stronger so they can stop a powerful Hollow - like being that is emerging as a major threat.
A plot might involve the Dragon Balls being scattered across the Bleach universe. Ichigo hears rumors about these powerful orbs and starts looking for them. Meanwhile, Goku and his friends also end up in the Bleach world while searching for the Dragon Balls. They meet the Soul Reapers and at first there's some tension. But as they learn more about each other's goals, they work together. The Soul Reapers are fascinated by Goku's power and training methods, and Goku is intrigued by the concept of souls and the afterlife in the Bleach world.