The F in an ABO Novel

Yi Jian transmigrated into a novel. The System promised him generous rewards, on the condition that he find the protagonist. Yi Jian: Could you give me some clues about the protagonist? System: It's an ABO novel. Yi Jian: Then... System: But no one knows what this ABO novel is about. Yi Jian: ... He calmly reasoned: Usually, if the protagonist in an ABO novel is an O, he's probably an O pretending to be an A who enrolls in school and gets into dangerous situations despite knowing his heat is about to hit. If he's an A, he's probably rich or powerful, with a terrible temper and an inflated ego, before falling for a B or O of much lower status. If he's a B, he's either capable and strong enough to rival an A, or so ordinary and meek that once he blends into a crowd, no one can find him again. System: Wow, you really know your stuff. Based on this analysis, the suspects included a certain Alpha, domineering, fond of pinning people against walls, and suffering from a whole list of protagonist symptoms such as insomnia and mysophobia. A certain Omega, an O pretending to be an A, with an irregular heat cycle who popped suppressants like candy. A certain Beta, with glasses and heavy bangs, who looked like a completely different person once he took them off. A transfer student, a streamer, a top student, a school bully, and plenty more. With protagonist-like characters springing up everywhere like mushrooms after rain, the System gave Yi Jian a golden finger to help him get close to all these reborn suspects: A special gender: F. Free, one size fits all. The ability to change one's own gender at will. Yi Jian: That's one hell of a golden finger. Thank you so much. Yi Jian: What gender would I turn into if an Omega marked me? System: I think you've lost your mind. Yi Jian: Then what if I marked an Alpha? System: ...I do have a new gender to recommend: Eginma. Yi Jian: ? Yi Jian: Then what if I marked an Enigma? System: I have Figema too. Yi Jian: Then what if I... System: Get lost. Black-bellied top who seems sweet on the surface, gloomy puppy-like bottom. One-on-one pairing, not a harem story. Lighthearted tone. The story itself is the final authority! Theme: Different people have different tastes, and no two people see things in exactly the same way.