Can anyone say what Yomi meant by whatever she said while beheading the fatty?
Back in the OG when that guy rp'd her, she was already bleeding a lot due to the hole in her stomach area. So the guy was commenting on how he can't tell whether she's a virgin or not. She didn't give him an answer back then, and she didn't give a straight answer now.
Fast forward to this chapter, and he's also commenting on how he's the only guy she's ever had. But now she comments on how he's not the only guy she's ever had. She doesn't confirm if he was the first or not.
Now, Yomi was supposedly born in the area of Amatsu no Yomi where the old hags dump their defeated soldiers. They only want virgins piloting the Mizunoha armor to preserve the nation's honor. She was removed from there after Mashiro's mom found her and made her Royal Guard leader.
Now we're getting into theory territory.
Of course, Mashiro's mom would soon be captured (and Aoka's mom petrified), leaving Yomi to take orders from the old hags. Without the sisters' protection, Yomi should be subject to the same rule as anyone else who got rp'd, stripped of her armor, whatever they're doing to the girls that make them act like empty husks, and dumped into that place again. Unless of course the old hags value her fighting prowess so much that they let it slide to keep using her as a soldier.
Yomi does display weird emotional reactions sometimes, or lack of. Sometimes, she also displays lack of sympathy to allies. Sometimes, it feels like her emotions are artificial. But it could just be her personality being strict and a little rotten. She's not an empty husk when Mashiro's mom found her (more like a wild animal) and during present day.
So my guess is that after the end of the OG series, she also did it with Nect. But if in a future chapter, the author somehow confirms they haven't done it yet, then maybe she really had her 1st time even before the OG scene with this guy.