He claims he doesn't care about appearances in terms of how "clean" he's doing it, but he also has an "oh shit" moment the minute he slips up and Seishin sees what a dirty tactic he used.

That it's followed immediately by a chapter of Sunako seeming to wonder what Muroi-san must think of their dirty methods, declaring herself unapologetic yet clearly in fact mindful of it is an interesting parallel.