I don't want to be your wife.

This book is also known as: "If Life Feels Hard, Try Becoming a Cute Girl!" Life isn't going well? As a boy, he loves anime and manga, but there's a pitifully thick barrier separating him from his "waifus." So, the boy resolutely puts on a cute dress and transforms into his own waifu! However, his parents disapprove, they argue, their relationship breaks down, and the boy impulsively leaves home. He'll have to go back after the college entrance exam, but how will he face his parents...?
"Still struggling? Then try being a girl! Don't wonder why, just go for it, kid!"
Thus, Su Mumu was transformed into a girl by a system that claimed to be an alien being, and appeared in the home of a disillusioned young man.
Thai Wind: What just fell from the sky? Oh, it's my girlfriend!