WARNING: The following contains spoilers for Boruto: Naruto Next Generations Episode 177, "The Iron Wall's Sensing System," now streaming on Crunchyroll.
With Ino wanting Inojin to choose his own path in the Boruto anime and not force himself to be a sensory perception ninja like her or his grandfather, Inoichi, fans can't help but notice how much he's like his dad, Sai. Apart from his pale look, he's mastering his scrolls and unique ability to bring drawings to life, which means he could become one of Boruto's most important allies in the future.
A highlight of this arc was seeing Sai advising him to be a hero, whether it be by following his artistic side or the Yamanaka clan Ino belongs to. As nostalgic as it is, it also harkens back to Sai's villainous past. With that in mind, let's dissect how he became a hero, forsaking Konoha's evil military so that he could shape a better village.
Sai was brought by the evil Danzō Shimura, recruited as a child after being orphaned, into Root, the nasty section of Konoha's ANBU police force. He was trained to be an emotionless operative ready to kill anyone deemed enemies of the village, whether it be women, men or children. Danzō wanted him to infiltrate Kakashi's Team 7 and slip him details as they hunted Sasuke down. As time went on, Sai coldly masked his true intentions with a facade of condescension and insults.
But as his duty progressed, he began to understand more about bonds and what loyalty meant. He came to understand the concept of family through Naruto, especially as the teen kept hope he could redeem Sasuke. It almost fell apart, though, when Team 7 discovered Sai was a plant who was really meant to work with Orochimaru to break Konoha, all so Danzō could assume power as Hokage. However, the snake ninja had Sasuke under his wing at that point and the relationship with Sai fractured, leading to him being exposed to Naruto.
Team 7 still kept faith in Sai, believing he had heroic potential. He'd beg to stay on with them, working to become a friend while giving Danzō the impression he was still a spy. Sai just couldn't believe people wouldn't betray each other so he learned a lot from Sakura, Kakashi, Yamato and everyone whose lives Naruto touched. He would soon realize Danzō was using him and wasn't best for the village, wanting to end the corruption he endured. As fate would have it, Sasuke would end up killing Danzō as part of his vendetta, breaking the seal that silenced Sai. Now, he could spill the beans on how Danzō was a tyrant, destroying Konoha from the inside, and this allowed him to truly become one of Naruto's closest colleagues.
Sai would work on the pursuit of Sasuke and Itachi, the fight against Pain and the Akatsuki, plus the recovery of the Tailed Beasts as Madara, Obito and Kaguya brought their war to the new shinobi world. He cemented himself in Naruto's alliance as one of its bravest warriors and when the war was finished, Naruto made it clear he was family too. He'd end up marrying Ino, someone also dedicated to the cause, to ensure the next generation had it easier and could carry on their legacies. As one of Naruto's closest advisors as Hokage and a Ranger at times with Sasuke, Sai has truly redeemed himself and as Ino and Inojin have noted, he's become very indispensable.