Isekaied As "Mary Stu"

an ordinary 30-year-old salaryman named yang dong gets transported into the role of the female protagonist in a mary sue harem novel. although in his own eyes he still looks like a middle-aged man, others see him as a lovely high school girl. now he’s falling into classic shoujo tropes and getting tangled up with the four male protagonists! how will he survive with his dignity?