This scene, kinda reminiscent of that iconic Neo vs. Agent Smith clone fight, would be even better if you could actually slash through these guys.
As Oh Seyoung shared, this is a part of his custom combat system inspired by Dynasty Warriors and built using DOTS Animation by Rukhanka. You can find more details about the customizations made to the Rukhanka Animation System here, and even download the playable build by clicking this link.
The developer also mentioned wanting to turn this into a full game and eventually publish it. Check out Oh Seyoung's YouTube channel for more progress videos: