A young girl named Miru and Ran, a boy who appeared before Miru, embark on an adventure in an alternate world — but something tragic awaits them there...

[Source: Anime News Network]

Story following Kuromi as she travels around the world in search of her missing sister, Romina, who makes her first appearance in this anime. In addition to Romina, a number of new characters will appear, including the friends who travel with Kuromi and a member of an evil organization that stands in the way of their journey.

[Source: Crunchyroll News; emended]