I have to admit, I laughed at Fai’s line at the end there. I didn’t think I’d be laughing in this arc.
But the fun thing about the “luck” angle (that it seems like Fai picks up on, though he might also just be mockingly derisive) is that this used to actually be a thing. At the start of the series Sakura’s luck was a force of nature and pulled her though a couple of interesting situations.
That’s not the case anymore. It’s been a long time since the luck has been mentioned at all, and more than that, nothing about the past few worlds has been easy or lucky for anyone involved. Sakura walked through the acid desert, on foot, injured, and with only a gun for defence. She fell down a cliff, hurt herself a lot, and had to climb all the way back up again. And then she had to walk all the way home again. Sakura’s luck has not helped her - it’s Sakura herself who got herself through that whole scenario by her sheer force of will.
And that’s exactly what she’s doing here, too. Nothing about these fights is luck; it’s all willpower, and the Random Cameo Guy (if he was smart) should know that no-one would be able to get through this competition on luck alone.
Either way, Kurogane takes offence at the insult to Sakura and (very violently) disagrees.
That pose at the end brings him very interestingly back to how he used to look at the start of the series, too. Which is interesting, because that’s the same way he would have acted whenever talked shit about Tomoyo.