Wakadanna-sama to Hatsukoi Kon: Kogareta Hito no Atsui Yubisaki

Today was suppose to the wedding day between Koharu's sister Akina and their childhood friend, the rich heir Sojiro Inukai. But for some reason, Akina disappeared, and now Koharu suddenly finds herself getting married to Sojiro instead!? This was her first crush...... that she had given up for the sake of her sister. But what if that love were to come true...!? Today, I'm going to be the bride for the man of my dreams. The cool heir of a high-class ryokan and the innocent daughter of a Japanese confectioner. It's a love story that's both sad and sweet, and it will set your heart pounding! (Source: Bunkasha, translated)