The Substitute Sister VS the Second Prince

As the Second Prince came of age, the search for a bride began. However, the younger sister who was supposed to go to the royal palace eloped the day before. What remains is an older sister who is so alike that she is mistaken for a twin. ……One month, perhaps? For just one month, why don't I act as a substitute for my younger sister? A participation work in the otherworld summoning collaborative project "Termia Stories +". (※Not an otherworld summoning as it is a bonus division participation) ※Also posted on other sites.