This means Seki is required to stay clear of any and all types of harm, large or small, throughout the whole run. Consider how many times you've played Elden Ring Runes and accidentally fell and suffered some fall-related injuries or gotten poisoned in a swamp. If anything like that occurs for Seki during his run, he's forced to start over. This turns a tricky and challenging game into an even harder beast to take on.
The success of the run is wild. Being able to watch someone complete Elden Ring in under 3 hours with their health bar not ever falling is captivating even if you (like me) don't have any interest in FromSoftware video games, and Elden Ring. (There is a point in the run when Seki wears a specific talisman that increases the damage and health of his character. In that moment, his health bar expands and it appears like Seki has been hit however this is only the way it works.)
Based on the streamster, who has run similar no-hit runs in other FromSoftware games, including Sekiro The streamer spent more than 130 hours just trying to achieve this no-hit, no-damage run. This involved planning, practicing and making a lot of attempts. In terms of the gear Seki prefers when attempting to defeat Elden Ring Items buy without taking any injuries, it's a simple kit that includes a fan-favorite Moonveil Katana.