Manga by author Watanabe Kana

From Chibi Manga:Morimura Nobara, 15 years old. Because of a fall from the cliff three years ago, she can hear the voices of animals. Once she got used to it, she notices that there's a guy's voice that says 'I can hear you clearly'

The protagonist Yukari and the twin brothers Shun and Ou have grown up like a family ever since they were children. However, their relationship begins changing on the first day of high school...?