I have found this game a while ago and played it for quite a long time cuz numbers go up me be happy, and by then I didn't manage to figure out how to finish the trail. Came back to the game after updating, added fucking shadow clone to my loop and finally finished the trail, and now I've put together a loop that gets me to a rebirth in around 5 minutes (with the offline time boost, but still not as optimized as it could be cuz I'm lazy) as the the Final Trail apparently becomes always available when I get to The Nest from the second rebirth on, which I'm not sure if it's intended since it took a long time to unlock it in the first rebirth
You need either some Charisma or Illusion magic iirc, not that sure tho since I'm currently always able to flirt with it apparently
Edit: Started a new run to test it out and the Flirt Shadow option appreared when I was levelling up Summon and Illusion, rather low levels but I'm not sure which one tho cuz it was sped up and I wasn't paying enough attention. Charisma is only to fuck it