@jdjohndoe13
I'm not sure if you're joking but SirGorillabitWithAHat was talking two
completely unrelated things:
1.the sea slug book aqua and kana were reading
2. the clue director kaburagi gave to aqua about the theatre company
your theory about aqua is interesting, but very unlikely because
1. Aqua is part of the main cast, the stalker is more of a side character.
2. Aqua is clearly considered a major star by the time of the movie, and his skill as an actor isn't specialized/limited to one type of character, so type-casting him as a stalker is unlikely
3. it's a re-enactment, not a copy: because ai was 20 when she was stabbed not 15; since the 15 years of lies is likely something original, so stabbing to death also has a high chance of not happening.