In a story set years in the past, Himura Yuu is a studious and diligent young man intent solely on maintaining his top academic position at Otowa Academy. One day, he meets a mysterious girl named Amamiya Yuuko, who, to his surprise, recognizes him. Memories of a distant childhood, memories rather left forgotten... meeting Yuuko again will force Yuu to confront the regrets and sorrows of their collective pasts and presents. In the present, Kuze Shuuichi may seem like a womanizer, but upon closer inspection, is a man who would rather be left alone. Hayama Mizuki, however, is not the type of girl who would let him be, especially after hearing the beautiful sounds of his violin performance. As Mizuki attempts to become closer to him, Kuze attempts to push her away—the tale of their budding relationship is darkened with undertones of an imminent tragedy.

Due to the influence of someone who visited her town when she was a child, Princess Mikoto of Elua decides to become a hunter and search for treasure all over the land of Driland. She sets out on her journey with her personal assistant Wallens, but they are soon joined by Pollon, a hunter who dreams of being a hero, and Paan, a wandering knight. As they continue their exploration they begin to sense great danger drawing near.

Hitotose Chitose is now living together with his 5 teachers as his mothers when a mysterious girl appears and becomes their neighbor which turns out that that person is Nagatsuki Kuron who wants Mu-chan to be her mother so another sibling rivalry ensues as to who would end up as Mu-chan's child.