Hatake Sakumo was skilled enough to teach Kushina a great deal. Almost every move he made was aimed at killing, and White Fang Swordsmanship was fast in its own right. Lightning Release chakra stimulated his body's cells to improve his reactions, while Wind Release Chakra varied the length of the White Fang blade, making its patterns impossible to grasp in combat.
Kushina was very fast in Nine-Tails Chakra Mode, but Hatake Sakumo's sword strikes were even faster. More than a decade of dedication to swordsmanship had put him among the very best.
Kushina kept getting the worst of their exchanges. At first, her carelessness left her with numerous cuts from the barely perceptible sharp edges of Wind Release Chakra in White Fang Swordsmanship. But she gradually adapted, especially since Hatake Sakumo also pointed out her mistakes, helping her improve considerably.
When Hiruzen Sarutobi learned of this, he wanted to stop it, but Hatake Sakumo would be leaving soon, and Kushina was beyond his control. Much as Hiruzen Sarutobi hated to admit it, Kushina in Nine-Tails Chakra Mode was no longer someone he could order around as he pleased. After some thought, he did not send anyone over.
Still, he sped up the reassignment of the Guardian Ninja, completing the personnel changes in just four days.
Although Kushina had only trained with Hatake Sakumo for four days, the combat experience she gained benefited her greatly. Hatake Sakumo was a speed-focused ninja like her, and there was plenty of experience he could pass on.
After Hatake Sakumo left, Kushina cut back on her training and gradually visited Karn more often.
"Boss, I'm starting to get somewhere with the Tailed Beast Bomb, but Tailed Beast Mode is still really hard. That Nine-Tails is such a stubborn mule. He curses at me every time