Owari no Kakera is an original story taking place one month prior to the beginning of the original game. It is told mainly from Akihiko Sanada's perspective beginning with him seeing a mysterious humanoid-shaped Shadow while exploring the Tartarus together with Mitsuru Kirijo. (Source: Megami Tensei Wikia)

Another world exists one level below the one we live in, the Rengoku. Rengoku is filled with a poisonous gas called "ren". Although "ren" is harmful to the human body, it brought many new possibilities to mankind. Artemisia also known as Alto is the first princess of the country Ei. She has an abnormal body which is a doorway connected to the Rengoku. Because of this her body emits "ren" uncontrollably, bringing death to the people around her. As a cursed princess, she is locked up in the castle's dungeon, living her life without daylight. One day Alto met a young knight named Fog and together they received an order from the royalty. Alto's goal is to become a "Rengokushi", controlling the exceptional power that "ren" brings. "Come, let us dance in the sorrowful Rengoku!"

A story about giving birth, not giving birth, and not being able to give birth.

Guitarist Kouhei is always fighting with his other band members due to wanting to go a different direction. Then while he's at a local music venue, he hears an incredible singing voice and falls in love at first "sound." He doesn't know who the voice belongs to or where it came from, but when X mysteriously appears, Kouhei unconsciously gets hard. He searches desperately to find him again, but his only clues were X's voice and a tattoo on his left arm. After several months with no luck, he runs into X by chance at the convenience store! Kouhei starts hitting on the man who introduces himself as "Rei," only to be completely rejected... (Source: Dogenzaka Shobo, translated) *Note: Originally serialized under the title "Looking for a Treasure".*