So I was thinking the other day how Minato developed the Rasengan. It apparently took him three years to study the Tailed Beast Ball to finally develop the Rasengan. Now this is an interesting bit of information as it was confirmed that Kushina suppressed Kurama's power the entire time she was a jinchuriki. So, the only other way for Minato to study the TBB, was from another tailed beast and/or jinchuriki.

The obvious assumption being that Minato fought Ay and Bee and Bee using a TBB against Minato at one point or numerous times. Isobu lurking around in the wild and Minato encountering him. Or Han being active in the Third War and fighting Minato. These are the most likely options that I can think of.

Does it make sense that Minato took so long developing the rasengan considering he probably had to get into a fight with Ay and Bee, Isobu or Han? Or was there some other tailed beast involved? Would Minato have developed the Rasengan quicker if Kushina was a perfect jinchuriki?

Share your thoughts down below.