In modern Japan, the sudden appearance of dangerous demonic monsters has caused widespread fear and unrest. These creatures attack women, and their bodily fluids are deadly when injected into the human body. This crisis has forced the development of a technology to absorb and utilize the demonic beasts' energy, but it is extremely unstable. To optimize this method and avoid wasting resources, the researchers developed the S-TRAN(C)XE system, also known as Succubusystem, which can recycle the absorbed energy into an improved suit. During the system's first human test, the research center is attacked by demonic monsters, causing chaos and the death of a girl. However, she later awakens as S-TRAN(C)XE, a demonic beast hunter.