Lunar Days Sim Date (2012)

In Lunar Days, the playable character, Karina had been having a recurring dream of being alone in the library with a book with a green colored plain cover in her hands; but every time she opened it, the dream would come to an end. As the dream started haunting her, she decided to start visiting the library regularly to look for the book. One day, something strange happened and she found the book. But as soon as she opened it, she was taken to another world, The Emerald World where 'day' and 'night' were seasons of 6 months. She loses the book that very day but it is returned to her the next day by the one who took it by mistake. It turns out that she can go back to her world only after 30 days, i.e., when the moon's full, just like the previous day.