“Imperfect beauty.”
The term comes from teachings of Buddhism, about the transient, imperfect nature of life itself. Wabisabi serves to remind us that all things are impermanent, incomplete, and imperfect, which means that perfection is ultimately impossible. Therefore, we should always try to see the beauty in everything. The philosophy is a central concept to both the language and traditional philosophy.
These aesthetics point to the overall theme of わびさび, with the concept of ones magical ability developing after a traumatic event in their life, a piece of beauty found in imperfection.
Junior high third-year Yokoo Hiwa, stumbles upon her classmate Tokumitsu Mitomo outside the school she longs to attend. Tokumitsu denies her involvement with the facility. However, after a series of unfortunate events involving Yokoo's selfish desires to learn of the magical world unfamiliar to her, she ends up miraculously saving Tokumitsu's life from a devil.
Yokoo and Tokumitsu are thrown into the world of magic and join Harumi Comprehensive High School to help protect innocent people from the dangers devils pose.
Powers manifest as a result of trauma, typically in a way which contradicts or abolishes the pain being caused. Depending on how severe the individual's situation is,—the stronger their emotions become—the stronger their abilities will be. They infrequently can cause mutations, and be passed down genetically. Powers first originated in America, which is why they're called パワー in Japan.
Devils (悪魔) are born after an individual gifted with a power passes away with regrets. They're violent in nature and resent those who wronged them, seeking revenge. The way to defeat a devil is by wounding their heart.
Angels (天使) are born after certain individuals die who hold strong regrets or have a strong emotional connection to one in the living world. They aid the people they were most connected to during their life. Angels do not posses powers during their human years, but may develop one after dying.
Faeries are born from flowers. They come in all sorts of classes and aid in protecting wildlife. Being born with some magical life, they're far more likely to develop powers as they begin their adolescent years. Most live in small villages in the Kansai and Touhoku regions. Fairies are distinguishable by their pointy ears and shiny translucent wings.
Witches live in a parallel world to ours where magic runs wild. Some will visit to aid in both killing and assisting devils. A few witches live in our world due to various factors, most are monitored by the Matsusei clan in some way.