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?