Saving 80,000 Gold in Another World for My Retirement 2 (light novel)

Having saved the kingdom from invasion, Mitsuha suddenly finds herself elevated to the rank of viscountess. Exploiting her world-jumping ability to the fullest, she’s now busy improving things in her new domain (with a little help from Earth’s advanced knowledge and technical skills). But with ballroom season on the way, it’s her obligation as a noble to return to the capital. Sure, the timing couldn’t be worse, but it might also present a perfect chance to showcase her new flagship product...