Is Kashin Koji actually someone who has appeared in Naruto before? So I've been reading the Boruto manga lately. There was this member of a secret organization Kara called Kashin Koji.

Many have speculated that he is


   Jiraiya


or his clone (or student/son, etc.)

They claim this because:


His appearance in front of Boruto and squad was with a toad summoning.
He knows how to make a Rasengan perfectly.


Does this theory have any credibility?
Sure, there are coincidences that Kashin Koji and Jiraiya could be the same, but you also have to realize that Jiraiya died and there was no way he was surviving after the fight with Pain.

Pain finished him and that was the end of Jiraiya, now where the Rasengan and the toad summoning comes into place, it could be very possible that he might have been a relative of Jiraya, but as it looks, we won't find out until we get more information.