Encountering Mugen at the brothel had been strangely not unusual and he would later find that he'd somehow been expecting it that night. The voice strangled with anger behind them was slightly more unexpected and its familiarity had caused both of them to pause and look. He had logically pieced together that from the location of the indignation that she was inside and part of the brothel and therefore dressed to part, but he had not been prepared for the visual assault such makeups would affect upon him.
He couldn't move for a moment, his uncontrollably wide taking in both her and likewise momentary inaction from Mugen. He was secretly thankful for this as it gave him time to try to collect his wits at the sudden and shocking intrusion. Mugen's smart mouth recovered quickly and saved Jin from any sort of placating response as he once again became immersed in action. Either Mugen had not seen what he had or he just wasn't impressed.
He hadn't been focusing on the other man like he should have for those first few moments, leaving himself horribly open in ways he would have been dearly reprimanded for in practice. But she had not been unpleasant to look upon. It had been a dramatic change from the scruff and dirt traveling brought, Buddha knows they all needed a good bathing, but it had suited her. In those few moments of face chubby with still clinging childhood set against that backdrop of the features of women rounded by maturity, he had seen the woman she would become. And while posing as such a prostitute had stung his manhood, he was glad she had not seen him degraded so.
From episode 4.