Despite Popi's curiosity, Neve could not tell her what he had in mind.
If he told Popi that he suspected Maren was from the same world that he came from, if he told her that he was going to use that suspicion to get close to Maren, Popi was going to crash out and find every way to stop Neve. She would argue with him. She would tell him it was too dangerous. She would refuse to let him pursue this plan.
And she would be right to be concerned.
Neve was being careless. He was not thinking before doing anything, which was definitely not recommended for someone in his situation. But he just did not know what to do. He was desperate. He was running out of time. He needed answers.
If Maren was a reincarnator like him, maybe Maren would know about those mysterious voices in the watch room. Maybe Maren would know about the system. Maybe Maren would have answers about how to go back to their original worlds.
