As I understand, many have theorized that minatos gift to naruto is the remaining yin chakra of kurama. Now what I'm wondering, is what if the yin chakra also contains the sound of the rikkudo sennin.... I say this because as we can see the physical (yang) energy of the rikkudo through narutos appearance when paired with kurama. Now if minato. Was able to seal his chakra in naruto. What if the rikkudo sealed part of his chakra in kurama through his yin chakra??? This would mean that the rikkudo may make an appearance and give naruto some insight as to what happened all those years ago. Let me know what you think. This is my first posted theory, please be gentle!!