Notes.

The narrative in Notes unfolds on Earth, set far into the future. Humanity's actions led to the planet's demise through pollution and warfare, causing all natural life to perish. The only survivors were humans, who managed to sustain themselves using advanced technology. Over time, they developed enhanced humans capable of surviving on the ravaged planet, alongside A-rays—genetically engineered beings that combined human traits with those of various extinct species. A conflict erupted between the enhanced humans and the A-rays, leading to further devastation of the already ruined Earth and pushing the enhanced humans to the brink of extinction. This war was abruptly halted by the appearance of eight Aristoteles, entities intent on annihilating all remaining life on the desolate planet. Note: This story is commonly known as Angel Notes. (Source: Type-Moon Wikia)