In Doumori, an imbalance of spiritual forces threatens to plunge the small city into complete chaos. Thankfully, for the students of Doumori Elementary School, new teacher and exorcist Meisuke "Nube" Nueno is determined to prevent the malignant spirits—known as youkai—from accomplishing their evil deeds. The first student who catches Nube's attention is transfer student Hiroshi Tateno, who displays inexplicable outbursts of anger, often lashing out at his classmates. When they find out that Hiroshi is possessed by a youkai, Nube manages to free his student thanks to the demonic power sealed in his left hand. However, a youkai hiding behind the appearance of doctor Kyousuke Tamano bursts onto the scene and quickly abducts Hiroshi. Helped by his student Kyouko Inaba and his expertise in the occult, Nube quickly uncovers Kyousuke's sinister plans. Rushing to Hiroshi's rescue, Nube will show once more that he will stop at nothing to protect his beloved students against all supernatural threats.

After the decline of the once robust fields of science and technology, a new energy source known as magic fuels the modern era. Humanity creates forbidden biological weapons: Gears. Those Gears eventually stand against humanity in a rebellion. Although they manage to overcome in the struggle for survival known as the Crusades, humanity's losses are so great that even after several decades pass, their emotional wounds remain unable to fully heal. Sin Kiske, the child of a human and a Gear, heads to his father Ky and mother Dizzy's wedding ceremony. Their wedding breaks the ultimate taboo: a union between a human and a Gear. Even with the world at peace, it took many years for such a ceremony to come to fruition. Despite the complex array of emotions surrounding it, the wedding ceremony is met with blessings. When suddenly, a mysterious girl appears... The fated child inheriting Gear blood–and the mysterious girl who despises Gears. Their meeting would shake the world.

Six childhood friends make a vow one day to become treasure hunters, and eventually grow to be the strongest heroes in the world. During his first quest, Krai Andrey realizes he isn’t cut out for the job. Even so, his friends make him their leader. Underpowered in the face of great expectations, Krai embarks on a reluctant hero’s tale of glory, headaches, and wanting to retire early.