I Became the Official Love Interest of the Urban Legend's Heroine

A soft-hearted girl transmigrates into the body of a mysterious, villainous man and has a daily meltdown while accidentally acting all cool in a world of supernatural mysteries. 🚬 My older sister is the powerful female lead of an eerie, supernatural world, an unstoppable heroine who rises through the ranks like a golden giant. I'm a useless transmigrator. Thanks to the sisterly bond we built from childhood, even though I'm a nameless cannon-fodder character in the original story, my life is still pretty happy. But cannon fodder is cannon fodder, after all. As time went by and the female lead was about to move on to a new area to fight monsters and level up, I let my guard down and met my end. As I lay dying, holding my sister's hand as she hurried back, travel-worn and unusually shaken, my eyes filled with tears. Sis, I'll be going on ahead. It happened in the time it took to close and open my eyes. I was alive again. Unfortunately, I had lost my flat chest and gained something else. I fell into deep thought. After a long while, I patted my own impressively firm pecs. The handsome, sinister man in the mirror copied my movements, then finally wore an expression of utter devastation. Sis! I think I've become your canon pairing! - ❣️ Third-person narration, no romance. A woman becomes a man, as a soft-hearted girl transmigrates into a seductive, sinister man. ❣️ There are one-sided crushes. Don't worry about gender or sexual orientation in this story. ❣️ He won't fall in love with his sister. ❣️ His outlook will grow and change, and he'll gradually adapt to his new identity. ❣️ An eerie world featuring mysterious games, livestreams, people reading too much into things, and low-fat content. Theme: Supporting characters are people too, with lives of their own.