Huh, we have vocative as well, but not for foreign names. John is John
in all cases, while only Ivan becomes Ivane (and some names are
naturally in vocative (and diminutive), like Yanko).
I want to add…
All foreign names (or words in general) “obey the laws” of Slovak language when they’re used in Slovak. Unless they end with some bazmek that it would sound weird if you tried to apply cases on it.
Kivi is in neuter gender. How would you create a genitive form? You can’t go with kiviho, because it would be masculine. It should end with -a, but neither kiva or kivia sound pleasing. So it’s always kivi. :p