Well, that's a really specific and interesting corner of fandom to ask about. Cray, as a character from the manga and anime 'King's Game', isn't one of the massive mainstream fandoms, so the fanfiction around him—and particularly the 'Cray x' ship, which I'm assuming usually means Cray/Reader or Cray/OFC—tends to develop its own distinct set of patterns. The source material's intense, survival-horror premise where characters are forced into cruel games really shapes the tropes. You see a lot of 'hurt/comfort' taking a very physical, high-stakes form. Stories often begin with the reader or an original female character being thrust into the King's Game alongside Cray. The trope isn't just about emotional reassurance; it's about literal survival, patching up wounds after a failed command, or sharing scarce resources. The comfort part is huge because Cray, in canon, is one of the more morally grounded and protective characters in that brutal setting, so writers amplify that instinct.
Another dominant trope is the 'shared trauma' or 'only sane person' dynamic. In a world where everyone is descending into paranoia and betrayal, fics love to pair Cray with someone who hasn't completely lost their humanity. They become a duo trying to outsmart the game together, strategizing and forming a trust-no-one-else bond. This often slides into 'enemies to allies to lovers' if the protagonist starts wary of him. A less common but fascinating trope I've stumbled upon is the 'outsider perspective' fic, where a character from our normal world gets pulled into the King's Game and their complete disbelief and modern sensibility clashes with Cray's hardened, resigned acceptance of the horrors, creating a great culture-shock tension.
Because canon leaves a lot of room for 'what happens after,' post-canon fix-its or survival continuations are big. Stories explore the two of them on the run, hiding from whatever entity was behind the game, building a fragile life in the aftermath. The romance in these is typically a slow, weary burn, born from dependency evolving into something deeper. It's less about grand gestures and more about the quiet significance of finding a safe place to sleep or a moment of silence without fear. The tropes here are less about fluffy conventions and more about the specific, gritty emotional logic of enduring an unwinnable situation together, which is what makes this niche so compelling to its writers.