Tooru Kirishima's notoriety is spread far and wide in the underworld. He is most commonly known as The Demon of Sakuragi—a man who is not afraid to resort to violence if deemed necessary. After almost jeopardizing a peace treaty, his boss tasks him with the most difficult job he has ever had: taking care of seven-year-old Yaeka Sakuragi—the boss' precious daughter—so that Tooru understands what it means to be responsible for another life. At first, the two do not seem to meet eye to eye, as Tooru has no clue on how to communicate with Yaeka, and the young girl is not used to expressing her emotions. However, as time goes on, they come to understand each other despite their differences. The fearsome right-hand man of a yakuza boss and the child he must protect are about to learn that family is not always bound by blood.

Ever since moving to an in-game world after countless hours of VRMMO grinding, Yuna now calls Crimonia—the city where she started—home. While maintaining her reputation as a renowned adventurer, she continues to manage her businesses; but most importantly, Yuna spends time with the people she has grown to love. Nevertheless, this world has a lot more to offer the carefree adventurer. It is up to Yuna to discover these wonders, and perhaps help more people in need as she encounters their various plights.

After fanatically playing the VRMMO World Fantasy Online for almost a year, the shut-in yet relatively affluent 15-year-old Yuna receives a bear costume from the game's administrators. The outfit, while somewhat embarrassing to wear, turns out to have overpowered stats and effects that make her character significantly more powerful. After accepting the bear equipment, she finds herself transported to another in-game world that prevents her from returning to reality. Confused and unable to log out, Yuna sets out to explore this new environment. She rescues a girl named Fina from wild wolves, who then guides her to the city of Crimonia. With her eccentric bear attire, however, Yuna stands out wherever she goes, and alongside her boosted fighting prowess, her reputation quickly rises—to the point that people give her the nickname Bloody Bear. Undeterred by this change in her life, Yuna decides to take on the role of an adventurer and fully enjoy herself in her new world.

During the dawn of the 21st century, the United Nations Kurobe Research Institute was established in Japan to investigate an ancient artifact, which was discovered during the construction of the Kurobe Dam. Scientists from around the world have gathered in the facility to study the object, while their children enjoy their everyday lives attending Mt. Tate International Senior High School. Yukina Shirahane, a reserved high school girl, is the daughter of the facility's head scientist. While visiting her mother at the facility, Yukina manages to solve part of the artifact's puzzle. To her surprise, what appears before her is Kennosuke Tokisada Ouma, a young samurai from the Sengoku era. As a threat approaches from outer space, Yukina, along with Kennosuke, finds herself defending Earth against the invading forces. Along the way, she discovers the mystery behind Kennosuke and the reason he is determined to protect her.