Dare ni mo Ienai

Born into one of Japan's most affluent families, Aoi has come to stay at a cottage with her favorite friends: popular model Yui, up-and-coming novelist Riko, and Olympic hopeful sprinter Himari. The four beautiful girls, each radiating a jewel-like brilliance, are about to reveal their "most cherished secrets" that they haven't told anyone else... You won't be able to take your eyes off the shocking "secrets" that these four girls reveal!!

(Source: Shueisha, translated)