Chihiro, the Masumi, and Iori vs Samura was less of a battle than it was an intervention for Samura

They knew that Samura would get violent, just like a loved one who's getting over an addiction or something.

Chihiro was basically acting as that 1 relative, who still has some sympathy for the person the intervention is for, but they're sick of their shit. Chihiro is like "look guys, if he decides to throw hands I'll step in. I'm not gonna be able to stop him but we'll figure something out."

The masumi then arrived, and they made some really valid points to Samura, while getting their shit mildly rocked for a few seconds, but they were serious about it. And Samura could tell they were.

Iori was the finishing blow, emotionally. She shlwed up when Samura was starting to get worn down in the argument, and threw cold hard evidence in his face