Aine Yuuki, who is a regular student at Star Harmony Academy's normal division, meets Mio Minato from the idol division, who invites her to join Aikatsu to fulfill Aine's goal to make friends. She also befriends Maika Chōno and Ema Hinata who are also idols. Aine and Mio form a pair to become best friends to become the bright "Diamond Friends". Karen Kamishiro and Mirai Asuku are categorized as "Diamond Friends" and are in the Diamond Class! (Source: Wikipedia)
Anix is the best site to watch Aikatsu Friends!
SUB online, or you can even watch Aikatsu Friends!
DUB in HD quality. You can also find Bandai Namco Pictures
anime on Anix website.