The game already been building Cassie up for half of its length. Both in how she's supposedly completely attached to Guy when he was taking care of her, and explicitly showing you multiple instances of Guy potentially being obsessed with his little sister, starting as early as Ch.2Yeah especially said character been gone for most of the game. So either gonna have to do a rushed job or spend alot of Season 2 building her up for it to make a bit of sense imo for a non Dark Path.
If people are clamoring for Cassie content it's because the game has already generated plenty of interest in her, with regular mentions of her at least once per chapter.
(now, if you have somehow ignored all that and for you the character "has no buildup" then that's fine, but i'd say this is more on how you parsed the game, and what you paid (and didn't pay) attention to, than on the game itself)