The practical method
Choose parents that already carry the passives you want, then breed repeatedly until the child lands close to the desired combination. This is a planning problem as much as a luck problem, because cleaner parent pools make the outcome easier to manage.
Why Yakumo matters
Yakumo is useful for passive-focused planning because it helps players think beyond a single child route. When the goal is a polished passive set, the route that preserves useful traits can be better than the route with the easiest parents.
Be careful with exact odds
Community discussion around Palworld 1.0 mentions passive changes and specialist cakes, but exact inheritance behavior should be checked against current data before publishing hard probability claims.
Clean parents make passive projects easier
Passive breeding becomes harder when both parents carry many unwanted traits. If possible, start from parents that already have part of the desired set and fewer distractions. A slower setup phase can save many eggs later because each hatch is easier to evaluate.
Know when to stop rolling
Before breeding in batches, define the acceptable result. Some projects need a perfect passive set; others only need one or two useful traits to move progression forward. Stopping rules prevent a useful Pal from being discarded because the original plan was too strict.