*Yin is opposite of Yang
Yang Kurama was always evil, mean, hateful
*Yang Kurama's chakra automatically mixed into Naruto's when Naruto was full of hate, anger, and dark thoughts.
Minato currently has access to Kurama's power while being pure hearted, happy, normal good guy
*Yin Kurama first words ever are Compliments! Yang Kurama never gave compliments until he was cnverted
mangastream "That was quite the TOUCHING speech your son just gave there... Minato" (addressed him by his name)
mangapanda "He became a NICE brat that really LOVES his parents... Minato"
Do you believe an evil bjuu talks like that? Those words were never in Yang Kurama's vocabulary.
*Yin Kurama acknowledges their is a difference between him and Yang Kurama
mangapanda "He was EVEN able to persuade my OTHER half"
Obviously meaning that the other half is harder too persuade or deeper in the darkness than himself
mangastream "Enough to move even this half of me"
Now im pretty sure its a small mistranslation but even if it isn't: After a few words and the Yin Kurama is moved? Lol Yin is definitely a good guy
Now lets not get anything misconstrued. Im not saying that Yin Kurama is fuzzy, loving, pet that does whatever another good guy asks. He is still untrustworthy & spiteful towards humans but personality wise he has a good heart, nice, and easy to get along with.
The light and dark of Yin-yang do not equate to good and evil. If anything it would have more to do with dominance and submission. Yang is dominant and Yin is submissive, it could be the Kyuubi's Yin is more agreeable than the Yang portion in Naruto was prior. That being said, it's still the Kyuubi and I doubt he's a completely tamed pup.