WARNING: The following contains spoilers for Boruto: Naruto Next Generations Episode 187, "Karma," now streaming on Crunchyroll.
Following the end of Boruto: Naruto the Movie, while many fans thought Boruto totally eviscerated Momoshiki Ōtsutsuki, the anime confirmed the villain left a lasting mark on the young hero -- literally. Boruto ended up with a small diamond on his hand, and, sadly, not even his dad or Konoha's scientists could decipher this cursed seal.
In the months after, Boruto began hallucinating about Momoshiki, though he had no idea why. Now, the anime's latest episode reveals what this mark is and the terrifying potential of its power.
After the sinister Ao is taken out for failing to kill Team 7 with his scientific ninja tools, Koji Kashin decides to finish the job so he could resume rescuing the Vessel Jigen lost. He quickly places Boruto and the young shinobi squad in a binding zone where electrified pillars render them immobile. However, as Konohamaru breaks out using a sealing jutsu of his own, it seems like the heroes can still succeed.
That is, until Koji unleashes high-level ninjutsu, using a Rasengan to counteract Konohamaru's. The soldier's stunned as this is something only a Konoha ninja could muster, but while he's distracted, one of Koji's toads attaches itself to Konohamaru's body, burning him up with a flame jutsu.
It's a horrendous sight, with Konohamaru screaming in agony as he burns, but it's also something Boruto has seen before, with the death of Mugino. Overcome with emotion, Boruto unintentionally activates the mark, which Koji confirms is the Karma mark: the seal the Kara terrorists have been working on. Koji's taken aback as only Jigen's subjects should have one, but as the black tattoos spread across Boruto and turn his eye blue, he realizes it's Momoshiki's power coursing through him.
Using this hand, Boruto absorbs the chakra of the sealing zone, disabling it. To top it off, he also sucks in the flames, stunning Koji even more. It's similar to Momoshiki sucking in chakra, except in his case, he could turn it into jutsu bombs and shoot them at his opponent. However, Koji's not in danger for long, as Boruto's body can't handle the sudden metamorphosis and he passes out.
Koji's fascinated with Boruto's sudden Karma activation and opts to let Team 7 go. He wants to see what'll happen to Boruto later on and, beyond that, he wants to discuss what transpired with Amado, Jigen's scientist. As for Boruto, while Konohamaru is grateful for the save, he's wary that this new change could kill Boruto as it clearly has an ill effect on his chakra flow and consciousness.