The Seventh Samurai is a world quest that is available in Inazuma.
However, to unlock the quest, you may need to finish the quest series Tatara Tales.
Here’s a walkthrough and guide of The Seventh Samurai in Genshin Impact.
After the Tatara Tales quest, you will meet Xavier east of Inazuma City. The location is shown in the map below, marked by the world quest symbol.
Talk to Xavier
You will see Xavier with Toranosuke. Talk to Xavier to begin.
Help Xavier produce a film
You will be given 1 minute for this quest. You basically have to stay within the boundaries of the circle for the entire duration.
To complete the quest, you have to defeat the three samurais and also get to the three marked spots in the area to “change position”.
If you fail the first time, talk to Xavier again. I experienced a bug where it doesn’t restart.
After talking to Xavier a few times, this portion manages to reload again.
The quest ends after this.