Kuusou no Sekai (空想の世界) is the main world of Nansei Project. It literally means "World of Fantasy". Its culture vaguely resembles that of feudal Japan with heavy Western influence, with a lot of folktale elements added on.
Thousands of years ago, a planet was created by an ancient being, and a land was created on that planet surrounded by a seemingly endless expanse of sea. That is, a land of fantasy.
- Kokunai Shrine (国内神社 Kokunai Jinja): A shrine located in the center of Kuusou no Sekai. It used to be the residence for the Kokunai clan, although currently only Miko Kokunai and Ritsuka Hayashi live there.
- Konsei (坤西): The capital city. A highly modern place with communities of humans and youkai.
- Totte Mitsumete's Mansion: A mansion run by the satori Totte Mitsumete that is used as a prison guard for dangerous criminals.
- Maid Cafe: A maid cafe run concurred by humans and youkai. It's the place of work for Aka Sakka, Lunar Tsubasa and Tokei Hijoshiki.
- Halloween World
- Secret Cave
- Military IYA (永妖軍 Eiyougun): The location for the Immortal Youkai Army. It's the place of work for the Gunso siblings, Reiji and Rena.
- The Hachirobei Sisters's Temple
- Akira Kurogane's Sky Temple (无明殿 Mumeiden): A floating temple at the outskirts of Konsei, where it acted as the residence for Akira Kurogane. After the events of Experienced Resident and Akira turning back into Akito, the temple is abandoned until it became the residence for Kirame and her minions.
- Lost Village (妙村 Myou no Mura): A village where humans and used to live 2000 years ago, before Kirame massacred the village. Since Mystical Lost Village, it's now a residence for youkai.
- Wonderland (ワンダーランド Wondarando): Another world.
- Northeastern Island (命目島 Meime no Shima): A mysterious island that recently surfaced. It’s rumored to possess unimaginable danger. It's the residence for Katame and her monsters, which are actually from Eria Kanrei.
- Gelida Mansion: The residence of Yukiko Egami.
- Core City: An underwater city populated by humans. It's ruled by the mermaid Mizugameza.
- Himeka Shrine
- Keika Shrine
- Fluvius City
- Wendigo Forest: A forest where the wendigo Mystical Ikimono hunts for humans to eat.
- Nebra Desert Village
- Desert Temple
- Fire Temple
- Kanrei Shrine (寒冷神社 Kanrei Jinja): An isolated shrine on top of a mountain. It's the residence of Eria Kanrei.
- X-mas Cafe: Another maid cafe, the difference is that this place is winter-themed due to it being next to the snowy lands. It's the place of work for Saika Noomu and Ruka Hinotama.
- Arakida Shrine (新木田神社 Arakida Jinja): A temple next to the Hills of the God, run by the merchant goddess Arakida. She can give anyone a new destiny and identity for free, as long as the customer pays. It's the residence of the Ochosan siblings, Arakida and Bijonu.
- Mayoi Shrine (眞善神社 Mayoi Jinja): A shrine that also works as a psychiatric booth, run by the fox goddess Mayoi. It's the residence of Mayoi Usanori and her daughter Michio.