WARNING: The following contains spoilers for Boruto: Naruto Next Generations Episode 180, "The Assassin, Mugino," now streaming on Crunchyroll.
Boruto Episode 180 takes a break from the Kara Actuation arc to instead dissect one of Boruto's mentors: Mugino. We've usually seen Boruto training with Sasuke, Konohamaru and Kakashi, but Mugino recently oversaw him in the field in the God Tree Clone arc, crafting a comedic dynamic between the pair.
Ultimately, while they annoy each other, there's still a lot of respect there. In Episode 180, we finally learn the full story behind Mugino's past and it's a very tragic one, reminding us of a heartbreaking issue from the Naruto era.
Boruto saves Mugino from some angry restaurant owners after the senior shinobi tried to run out on a tab. Mugino admits he spent his salary on a sick child but after Boruto pays off his mentor's bill, he's cynical about how true this is. Mugino, filled with jokes, takes him home, however, as he needs a favor. There, Boruto's taken aback when he sees that he lives in simple conditions, realizing there's more than meets the eye.
A picture of the Third Hokage, Hiruzen Sarutobi, kickstarts a deep conversation, in which Mugino confesses he chose this location as he gets to look out at the mountain each day that has the Hokages carved into it, including Hiruzen. Mugino was an orphan from an outside land whose parents died due to wars plaguing so many nations during Naruto's teen years. In the flashbacks, two rogue shinobi found him and turned him into an assassin, using a seal mark on Mugino so that if he didn't kill Hiruzen, he'd pay the price instead.
As a result, Mugino infiltrated Konoha as Hiruzen was offering citizenship to refugees fleeing war-torn areas, and after pretending to bring him flowers a night, he attempted to stab the leader. Hiruzen caught the boy in the act but realized he was a victim, reminding us of the Akatsuki origin. The master ninja then used a shadow clone to take Mugino's bosses out, and then, after empathizing with Mugino, he gave the kid a hug. It's a very sentimental moment as he promises no harm would come to Mugino, giving him documents to officially make him a Konoha resident.
Mugino, still rocked by how he was used as a weapon, took a couple of years though to come back. By that time, Orochimaru had already killed Hiruzen -- his former mentor. This inspired Mugino to join the ninja school and become like his hero, someone he saw as a father-figure. At the funeral, he'd see Hiruzen's grandson, Konohamaru, crying but Boruto's further stunned to find out Mugino never revealed his past as he and Konohmaru became friends. The senior's ashamed of what he did but if Konohamaru could forgive Orochimaru, he'd do the same to Mugino.
Episode 180 ends on an uplifting note as Mugino wants Boruto to look after his apartment and pet turtle, showing there's now trust between them. And to top it off, a boy comes by to drop a gift for Mugino later on, confirming he used the mentor's salary for medicine for a sick sister. This leaves Boruto inspired by Mugino's compassion and kindness, realizing how lucky Konoha is to have his services.
