The video, which appears to be an in-progress, Spanish-language version of the short, was initially uploaded to YouTube by a user named Kuriboh cervantes, who claims to be unaffiliated with Blizzard. Where they got the video is unknown, but its legitimacy is beyond question. Everything from the art style, to the quality of the animation, to the emotional beats screams Blizzard.
The cinematic follows Kiriko as she returns to her mother's home, briefly saying hello to an employee in the hotel and his deaf granddaughter. When thugs from the Hashimoto clan arrive and begin antagonizing the two, Kiriko rushes to their aid. She teleports around, throws two knives to incapacitate one thug, places a glowing yellow paper on the injured grandfather to heal him, and, at the end of the video, conjures glowing blue torii gates that seem to make the old man and his granddaughter faster and stronger.
It's plausible these actions correspond to Kiriko's abilities in-game, with the torii gates likely her ultimate ability. She will be Overwatch's 35th hero.
Kuriboh cervantes' upload of the cinematic has since been taken down, as have several mirrors, but as of writing it remains viewable here.
Blizzard has yet to officially confirm Kirikio's likely imminent reveal. The company recently clarified that new heroes in Overwatch 2 will be available as unlocks on the game's free battle pass, but did not say whether or not they would be directly purchasable.