@shadolord If you wanna kill the NPC, just go for it. Might as well do a bit more to get the story going a bit faster.
So I had a thought, and figured I'd run it by everyone here before putting it into practice:
In Light's introduction post, it was implied she'd killed a rookie from the academy. I was thinking it'd be interesting if Kaede knew that 'newbie' and has a reason to hold a personal grudge. Whether or not the Gotei 13 (and Kaede herself) knows who the killer was doesn't matter so much; it could still be an unresolved incident, but it'd give something to build off of.
she didn't want another skirmish with an academy newbi who had a strange notion of attacking her on sight. It was a shame too, Light'd more than happily sit down and have an idle chit chat with them if they had offered, but no, she had to accidentally knock his head off. And unlike the hell people, the soul reavers didn't regenerate at all.
Oh I'm totally fine with it being a mistake, that's how it felt during the initial reading. Togabito are strong, and automatically res/regenerate, so it makes plenty of sense that Light might have killed a shinigami on accident. I just had a sinking feeling for a moment that the recruit's death was going to be played off as completely unrelated to her when you mentioned the stair thing.
TL;DR I like the idea that she didn't understand how fragile 'normal' soul reapers are, and will be riffing off of that. If Kaede ever learns of Light's connection to the dead recruit, she will probably still hold her responsible for it, regardless of whether or not it was a mistake or accident.