In order to take over her grandmother's Dagashi store, art student Kumi Honamanuma moved to Kyoto. She met Harami Mino, K Kusanagi, Mai Haisaka, and a dog who lives in the store, which supposed to be empty. Kumi ended up living with these girls, who claim that they are heroes reincarnated to contemporary period to chase after the demon king. Harami and others seem to live in a peaceful life with no missions to to do anymore, Ran, who was demon king in the past and appears to be an elementary school girl from failing to reincarnate, one day. The story begins with Ran requesting to collect demon king's fragments.

The story centers around a timid orphan named Mizumura Shinta who goes to a missionary school in Tokyo. His seemingly normal life changes when a beautiful half-human Romanian girl named Lilith suddenly transfers into his school. Mizumura discovers that he is actually a vampire hunter and the successor of the Romuald lineage.

The "Otherworld" is a vast and dangerous realm hidden from the knowledge of the common folk. It is also home to many creatures that threaten any human who dare visit it. To witness its desolate yet oddly absorbing environment, one must search for portals that could reside anywhere, from secret elevators to shrine entrances. After a fateful encounter with a horrendous Otherworld denizen, Sorao Kamikoshi ponders whether to keep going or give up in life. Meanwhile, Toriko Nishina scours the Otherworld in hopes of finding her friend Satsuki, who she believes is lost somewhere within the realm. When the two cross paths, friendship blossoms. In order to acquire as much information about this obscure dimension, the two travel back and forth from the real world to the other. Sorao and Toriko's bodies are soon influenced by the Otherworld, preparing them for the many horrors to come as both of them try to fulfill their goals.