Death March to the Parallel World Rhapsody, Vol. 18 (light novel) by Hiro Ainana

After dispatching the monsters laying siege to the royal capital and aiding in the bloom of the Royal Sakura blossoms, Satou and his party are finally able to welcome the new year. But even more exciting than New Year festivities is the auction surrounding the Ring of Prayer! If Satou wins the bid, he might just be able to free Arisa and the others from servitude!
Binding: Paperback / softback