In the latest episode of Boruto Naruto Next Generations, Boruto Uzumaki’s teacher in Sasuke Uchiha, has suggested his pupil should undergo some special training to further advance his Rasengan. This is interesting as Boruto already wields an unusual Rasengan, which disappears before striking a blow against his opponent.
Now, with Naruto occupied, as well as Minato and Jiraiya dead, the only other characters that we know of the can use the Rasengan is Konohamaru and Kakashi. Konohamaru is a Jounin and leader of Boruto’s team but he has already passed down his knowledge of the Rasenbgan to Boruto, while the latter has not.
Kakashi may not wield the Rasengan as his primary Jutsu of choice like Konohamaru but because of his knowledge in the Jutsu from his master Minato, as well as his former copying abilities, it allowed him to train Naruto. This is why he was able to help Naruto apply his wind-style into the Rasengan, a technique that even his master and Naruto’s father couldn’t accomplish.
Now, it appears as if Boruto will undergo similar training. However, this should normally take Boruto longer, as he cannot use the same number of Shadow Clones as Naruto to speed-up the learning process and Boruto doesn’t have the same healing abilities Naruto has, which means that Jutsu could hurt Boruto permanently.
Although, it’s possible that Boruto’s Karma Mark may be the edge Boruto needs to access more Chakra for extra Shadow Clones and also rapid healing. As for Boruto, possibly losing control, we know that Wood-Style can hold-back Naruto when he underwent this process, maybe another Wood-Style user like Yamato or Moegi can help Boruto if he was to lose control.
Sasuke will also be there and just abilities can also subdue Boruto if something was to go wrong. As for it being the Rasenshuriken, it’s possible but it’s also possible it could be a whole other Jutsu. Though, Boruto is most likely learning version of a disappearing Rasenshuriken. Boruto’s Rasengan can either fuse, wind, lightning and water release, as that’s what he’s affiliated with.