The story centers on a young man named Yuu Haruna who has just switched schools. He's a bit shy, and he's constantly glued to his smartphone so he can check Twitter. He meets a girl named Fuuka Akitsuki, who doesn't even have a cell phone, is free-spirited, and naturally fascinates others. Yuu recently has been getting back in touch via Twitter with his childhood friend Koyuki Hinashi, who is now a popular singer. One day Yuu invites Fuuka to one of Koyuki's concerts, and there the three meet for the first time. The story follows the love triangle between a love that started through electronics, and a love that didn't start through electronics.
Summary taken from: MyAnimeList