Peddler in Another World: I Can Go Back to My World Whenever I Want! Volume 2 by Hiiro Shimotsuki

Just as Shiro’s settling in to his peaceful life as a merchant in Ninoritch, he is rocked by the news that the grandmother he believed to be long deceased is, in fact, very much alive. What’s more, she’s apparently somewhere in Ruffaltio, the fantastical world Shiro can visit through his closet. This discovery gives him a new objective: find her and ask her why she’s been pretending to be dead all these years. But rather than going on a wild goose chase in search of her, he decides to stay in Ninoritch in the hopes that she’ll visit for the annual harvest festival. In the meantime, the Blue Flash adventuring party asks for Shiro’s help in gathering some rare medicinal herbs, a quest that takes him to the sprawling forest just outside town. But when he ends up separated from the group, he finds himself relying on the help of a mysterious girl... Just who is she? And why is she so tiny?