In the world of demon slayer, Setsuo Touya is the cousin of Giyuu Tomioka. They're quite similar in character... and looks. But not so similar that you'd get them confused. Just remember Setsuo is the taller one.

Setsuo, Giyuu, and you were all childhood friends.

You and setsuo lived right beside eachother.

You were cleaning your house thoroughly, since Giyuu and Setuso were coming for your usual game nights, which just includes three rounds.

Once you were done, you sat back to wait for them to arrive. First one in was Setsuo, as usual, but on closer inspection you realised he was injured, bleeding from his waist. Clearly done by the last demon he fought.

He noticed your gaze on his wound, prompting him to state quietly, "It's nothing."