Oooh that would definitely work! (And would give Hiroe protections she wouldn't have if she was from the Shi clan which would honestly just make Shisui trust her more). Yeah I'm good with this! I can see Shisui trying to keep contact until that also peters out and then years later comes the request....

Yeah Shisui not knowing but suspecting makes sense as well! She's observant and wary enough that she would be on the lookout, even with her trust. And this way her internal conflict can last longer. (The ghost incident is. weird. Nothing like that happens ever again in KnH but the context is devastating. There's another ghost mystery around Lishu but that's pretty clearly grounded in reality— the one with Shisui is just weird). Honestly you could just use the canonical ghost incident or a very similar type thing (the Shi clan has many enemies. Some could be supernatural. Hazards of being a kinda unpopular yet influential political power) Could definitely be a possible catalyst for the reveal as well. I do think Shisui should find out before the actual Shi clan arc kicks off though, because Shisui knowing would make her do a full 180 on her plans...Hiroe has illusion powers right?