I've rescued Jenny from the frontier post using Kurohime, slept with her, but now it feels like the script is broken. Flaire only says she's thankful for Jenny being safe, and doesn't start the second assault at the assassin's guild. I speak to Nori and Moriko but I simply cannot unlock their good scenes. Does anyone knows about this? I just need this to 100% the game.

did you talk flaire in thief guild after you done saving jenny from prison?

If you did go police hq talk cheif of police and talk commader in white citadel and talk cheif police then should be able talk flaire i think set trap for thief guild and assassins guild