1x11 - In/Spectre

Kotoko came up with three solutions, but they all got shot down. Kuro keeps trying to grasp the future where they can defeat Steel Lady Nanase, but Rikka made it disappear once again. But Kotoko wasn’t done yet. Steel Lady Nanase is not a ghost. What is Kotoko’s 4th solution that may finally put an end to Steel Lady Nanase’s existence once and for all?