Jiraiya likely pieced this together by observing Sasuke's extreme interest in Naruto, his reaction to the Kyuubi's power, and his mastery of advanced ninja knowledge. 5. Production Details
Boruto is struggling with fear after seeing young Naruto lose control of the Nine-Tails' chakra in a previous fight. This trauma makes him recoil from Naruto, preventing them from syncing. (Dub) 132 : Jiraiya's Assignment
At the end of the episode, Jiraiya approaches the mysterious traveler and bluntly asks, "Are you Sasuke Uchiha?" . Jiraiya likely pieced this together by observing Sasuke's
Sensing Boruto’s hesitation, Naruto feels deeply guilty and becomes unable to focus properly on the training. 3. Key Character Moments his reaction to the Kyuubi's power