Ane Kurabeあねくらべ ; 姐姐竞赛 ; 姐相随

From MangaHelpers: Shun knew what to expect when he became a high school student. As he entered the gates of his new school, four beautiful girls suddenly surround him. These four girls are the same four girls he grew up with since kindergarten. The four girls are Rio the athlete, Miku the cook, Nana the nerd, and Yuri the student president. These four girls will be battling it out between them in order to win the heart of their beloved Shun. [DrCoke]