Just randomly decided to play this again out of nowhere and realized how the last CG of base game parallels the poster art of ST so I looked up threads here discussing this topic and seen mixed opinions and other users who brushed the whole thing as a messy inconsistent prologue storytelling. I was gonna agree with the latter until I remembered a few small key details and everything started making sense lol.
Now if I'm remembering our Imouto's lore correctly, Bro mentions how her white/silver hair is another result of her illness but I don't remember if he mentioned her original hair color since he brought up their mother as subject of comparison. If Aidelle is really Imouto, then I believe there is no retcon or inconsistencies, and her original hair color could be blonde for all we know. In the last episode of the DLC timeskip, I think we are in one of the rooms of Aidelle's Inn. And there when you go to click on Panty collection and read on Imouto's stats, her summary changes, and you could see her all grown up looking exactly like Aidelle. As mentioned in the last CG, Bro, along with Imouto and Kana, left the town and embarked on a journey for reasons regarding Imouto's treatment possibly. Now in Bro's summary, we got a little extra detail stating that Imouto has been distancing herself from him and giving him the cold shoulder. This is likely her maturing and learning she's not supposed to have sexual relations with her brother lol. So maybe it's not a stretch to say that the whole "childhood friend" thing Aidelle says is just the full extent of her totally distancing herself from bro. And to fully support this belief, I remember when Bro blew his load in Aidelle, she says something along the lines of "why did you do that when we're siblings?"
As for Kana, I believe Kana and Kodachi are the same person. Heck, Kodachi Kana could be her full name if the latter isn't her nickname. Her fighting style (complete BS), competitiveness, and personality mirrors Kana perfectly.
Lastly, we have Yui. No, I don't believe Yui and Medina are the same person. I don't think this needs to be said again but if anyone still believes so, it just doesn't make sense. We just don't meet Yui again for the 'first time', and Yui wouldn't be so innocent about sex when she was engaging with Bro in the DLC. Even personalitywise, they're nowhere similar. She's just not in the epilogue, as clearly stated in the last summary that only Kana went with siblings on the journey.
And that's it for my long interpreted conclusion that nobody asked for. Unfortunately, I don't have the screenshots anymore to back up any of what I've just said and I'm only going by memory, so feel free to correct me if I've said anything false. It's too bad the rest of the cast (Kasumi, Yui, Yukari) aren't included in ST but hopefully, they make an appearance in Inusuku's future games.
