WARNING: The following contains spoilers for Boruto: Naruto Next Generations Episode 188, "Awakening," now streaming on Crunchyroll.
As much as the Boruto manga has touted Kawaki as a tragic character, the source material always felt light when it came to his origin story; specifically, how Jigen altered his genetics to make him a lab rat. It did add an air of mystery to the teen, admittedly, but there was still was a lot that could have been shown regarding his past to contextualize the despair and the tough road he's walked.
Episode 188 of the Boruto anime just made up for this, however, and as more details about Kawaki's origin unfold, we experience some devilish insight never seen in the manga -- insight that truly paints a tragic picture of abuse.
In the episode in question, Boruto and Team 7 stumble on Kawaki after Koji Kashin has killed Ao and whipped them in battle. As they try to figure who Kawaki and what his role with Kara is, we're provided with flashbacks that reveal how the Vessel fell into Kara's lap. One segment covers a piece straight from the manga wherein Jigen's bartering with Kawaki's dad -- a drunk in a bar. The kid's almost passed out on the floor, tired, hungry and thirsty, as Jigen quite literally purchases him. Once the deal is done, there's an ominous declaration from the boss that he's Kawaki's "father" now.
But it's the new lair scenes -- not from the manga -- that truly show a side we didn't know Jigen had. Kawaki wakes up off the floor and struggles to get to his feet. He's beaten and bruised, only to walk into Garo, who's shocked that the boy's alive. It turns out the experiments were dumped here and it's implied those that were barely alive fought each other, often to the death, to prove to Jigen they still had something to offer.
This leads to Garo and Kawaki brawling and the kid blowing Garo's jaw off. Shockingly, Amado and Koji are spying on all this as if it's a game and this is their gladiator's arena. It's Jigen's way of having his generals assess these soldiers, not caring if kids like Kawaki are famished or damaged, or if the likes of Garo need aid. In fact, both are physically and mentally fractured, further emphasizing that the participants are nothing more than expendable guinea pigs, or puppets. This also explains why Amado's lab is filled with giant vases that act as medical receptacles.
It's heartbreaking seeing Kara pushing and grading young, inexperienced warriors like Kawaki in such a manner, especially as the warlords don't even tend to him after the scrap. In fact, the way Amado celebrates the boy and his Karma mark -- hyping him up as the weapon Kara wants -- really adds to their terrorist image. (This revelation also explains Code's role, as well.)
It's highly apparent they have no qualms about using child soldiers. It's no wonder when Kawaki subsequently wakes up in the forest, suffering nightmares and PTSD of the lair in present-day Boruto, he doesn't trust the Konoha-nin. All he's known is hurt and betrayal.