The shortest possible version of the story is that some malignant bullies (called the Tandere Bitch Club) made up the take “you can’t be kin outside of your race” in around 2015 and went around spreading it in the community.

It was discovered that they were white themselves while claiming to be Japanese and did it to “keep all the anime characters for themselves” basically.

“You can’t be kin outside your race” is an extremely racist and bigoted take because whether you believe being fictionkin is supernatural or psychological, what you are saying is that people outside of your race are so foreign and incompatible that people of another race cannot understand their experiences, or if you believe in reincarnation, that souls are locked to one race forever.

They were also bullying and harassing people to “drop” and stop having “problematic” kintypes which is simply not possible to do and also is extremely ableist if you believe that fictionkin is a psychological phenomenon.