The Equipment: Living Forms, or ELFs, were created over fifty thousand years ago to assist humankind in their combat against the Honkai—the decay. With the project's success, the ELFs soon became sentient, compelling humanity to treat them as near-equals. However, when the Ninth Herrscher laid waste to the planet, almost all traces of ELFs vanished into the Sea of Quanta's endless abyss.

Yet, there seems to be a bubble universe where the ELFs' fate has taken a brighter turn. Here, they live peacefully among humans and attend a specialized institution, ELF Academy, where they study as if they were human beings themselves. From Selune's Elegy's chuunibyou tendencies to Blood Embrace's "gangster" shenanigans, the peaceful environment of the academy is guaranteed to provide relief from the depressing state of the main universe.