I'm sure it wasn't that bad for Suzuno. If any guy was gonna see her accidentally changing clothes anyway, Tsukuru being that guy would be the best case scenario for her.
There we go, Black Mist/Kurokiri's human form. A manly man and not your typical sword loli/sword mommy. Interestingly, even Tsukuru himself pointed out the cliche.
He has more than enough waifus already, so I hope this guy can at least be his best friend. Whatever happened to male leads having male friends? It's like it's not even allowed anymore these days... like jealousy tropes have poisoned the minds of readers and authors, making it some kind of "unsafe" choice to do in a story.