Seiji is a normal male student without a girlfriend, except that he has strange dreams almost every day. One day, he was going to be reunited with his younger sister whom he haven't seen since they were small. However, not one, but five younger sisters were waiting for him! It happened that some incident caused the protagonists from different parallel worlds to disappear and their younger sisters went searching for them. All of them ended up coming to Seiji since he was the same as their brothers. At the same time, strange dimensional distortions started appearing around him, threatening the balance of all the worlds. How will he and his younger sisters confront this crisis?