Hatsuki is a highschool student living with her sister, Hatsumi, who she has a huge crush on. On Hatsumi's 16th birthday, she is suddenly surrounded by a green light and disappears in front of Hatsuki. She manages to follow Hatsumi with the help of a being resembling a fat baby chick (literally), ending up in a place called "The Great Library", which is full of different worlds stored in books. Hatsumi wasn't there, though, so the search for Hatsuki's great love begins and involves traveling from book to book. (Source: AniDB)
9Anime is the best site to watch Yamibo: Darkness, The Hat and the Travelers of the Books
SUB online, or you can even watch Yamibo: Darkness, The Hat and the Travelers of the Books
DUB in HD quality. You can also find Studio Deen
anime on 9Anime website.