Yo-kai Watch 2
Yo-kai Watch 1
IV stands for Individual Values.
IVs are present in Yo-kai Watch. IVs are determined immediately after befriending or recruiting a Yo-kai. Newly evolved or fused Yo-kai are treated as new IV. Newly Evolved/Fused yo-kai will adopt stats as though they were leveled from start-to-finish as their "default" Attitude, just like freshly recruited Yo-Kai do.
"IVs" are balanced out, so unlike Pokémon, you cannot simply have one Yo-Kai with "perfect stats" all around. However, IVs placed into stats that are naturally high on the Yo-Kai have a bigger impact than those placed in lower stats. This was already known from my experiments into IVs in the past, but it's confirmed now.
"IVs" from pre-evolved forms DO matter for the evolved/fused Yo-Kai, but it is not a direct translation. The newly evolved/fused Yo-Kai will have its own "IVs", but will incorporate the "IVs" of the pre-evolved/fusion material Yo-Kai into its stats as well. This is contrary to what was formerly understood in my guide.
There is a special "Tribal IV" separate from the "IVs" of each base monster that raise a particular stat extra for each Tribe. For example, all Tough Tribe members have a bonus "IV" level for Defense that can really jack up that stat.