WARNING: The following contains spoilers for Boruto: Naruto Next Generations Episode 187, "Karma," now streaming on Crunchyroll.
Episode 187 of Boruto finds Team 7 in major trouble after Ao's ambush cost them Mugino. Despite regrouping and defeating Ao, they're left badly wounded from the brawl. This makes it easy for Koji Kashin to sweep in and try to eliminate them so he can recover the Vessel and restart Kara's plan for world domination.
However, while the heroes were accustomed to Kara's non-shinobi operatives that were more focused on scientific tools, they're left speechless in this battle, when they discover that Koji's power has a surprising connection to Konoha.
Koji doesn't hold back at all, using a sealing jutsu to bind Boruto, Mitsuki and Sarada as he attempts to finish the job Ao started, creating a field of pillars crackling with electricity, rendering the team immobile. However, Konohamaru has a special seal of his own and he breaks out, wondering just who on earth Koji really is. The fact he summoned a giant toad upon landing is shocking, as it's a move just similar to one the likes of Naruto and Jiraiya used back in the day, intriguing Konohamaru as he gauges Koji's abilities in battle.
However, Konohamaru underestimates Koji, who turns out to be the better fighter, using ninjutsu and taijutsu like an expert. Now realizing what he's up against, Konohamaru presses further and finally senses the enemy's off-the-charts chakra levels. Basically, Koji's not a warrior Konohamaru can take, especially not in his injured state -- but he has an equalizer. Konohamaru unleashes his trump card, the Rasengan, but much to his surprise, Koji has one too.
They both push the energy balls at each other, creating an epic stalemate of a moment. But this raises a lot of questions. The Rasengan is a move only Jiraiya, Minato, Kakashi, Naruto and Konohamaru can pull off. It was passed down the Konoha line in this order, which means Koji either copied it or learned its secrets from someone in the village, suggesting there could be another traitor within Konoha. Or, Koji could have lived in Konoha in the past, either way, Team 7 is desperate to figure out how could he learn such an exclusive move.
That said, as both bombs cancel each other out and blow the men away, Koji once more pulls off a brutal move using his toad. He attaches it to Konohamaru and lights the warrior afire, but luckily, Boruto's able to break free and help his mentor out. Still, after realizing these heroes have no idea where the Vessel is and that he's actually wasting time, Koji decides to leave. He commends the team for a nice sparring session, as he barely broke a sweat, leaving them worried over who else knows the secrets of Naruto's inner-circle.