The Prince in His Dark Days Vol. 1 (manga)

A heartrending modern love story. A drunkard for a father, a household of poverty… For 17-year-old Atsuko, misfortune is all she knows and believes in. Until one day, a chance encounter with Itaru–the wealthy heir of a huge corporation–changes everything. The two look identical, uncannily so. When Itaru curiously goes missing, Atsuko is roped into being his stand-in. There, in his shoes, Atsuko must parade like a prince in a palace. She encounters many new experiences, but at what cost…?