The Fantastic Garden

The Fantastic Garden (空想庭園) is a series by Story Researcher (cosMo(暴走P) and GAiA). cosMo composed the music, Nanashi assisted with certain illustrations, while GAiA collaborated with cosMo in some of the lyrics.

Currently this series has ended.

Background
Possible (unconfirmed, however heavily hinted) prequel to The Girl's Fantasy Cinema (少女の幻想劇場) series.

A girl creates a utopia "Fantasia" for the heroines of various stories, where they will no longer be burdened with everyone’s dreams. As this utopia grows out of her control, is it really the best place for anyone to be?

Θ (Capsule)
Sung by Hatsune Miku A strange fad has been going around associated with θ (theta)... A girl (nicknamed Shii-tan by fans) is given a θ 'capsule' by a strange gentleman, which she describes as having "a sweet and fun taste." She begins to see and feel strange things, like fish flying in the sky, the sky and sea melting, and the feeling of sinking. She feels happy, yet alone, and realizes she loves the whole world.
 * Nicovideo Broadcast
 * Youtube Broadcast

少女の空想庭園 (The Girls' Fantastic Garden)
Sung by Hatsune Miku Sent by high-frequency radio waves, please do take care. A girl with a feathered pen wants to create her own continuation of a story. She creates this absurd world - The Fantastic Garden "Fantasia" - where the heroines from other stories are free from the burdens of being relied on by others.
 * Nicovideo Broadcast
 * Youtube Broadcast (with Subtitles)

園庭想空の女少 (Anti the Fantastic Garden)
Sung by Hatsune Miku and Kagamine Rin The Girl begins to criticize herself, feeling that her creating the Fantastic Garden is only a way of asserting herself, or perhaps self-fulfillment. When this world ends, what would be left? She becomes angry, and breaks the pen that she created the world with. The Girl, powerless, is swallowed by the "Shadow" - the Fantastic Garden...
 * Nicovideo Broadcast
 * Youtube Broadcast (with Subtitles)

ミヤコワスレ (The Forgotten City / Storyteller)
Sung by Kagamine Rin In the Country of Light, a Girl is granted the Sword of Moonlight, and tasked to repel the soul-stealing fog that plagues their country. She heads to the Country of Night, wherein lies the Ruler of Night, a goblin who had created the fog. Though she bravely plans to oppose him, the World of Light is swallowed by a strange darkness...
 * Nicovideo Broadcast
 * Youtube Broadcast

空想庭園依存症 (Dependence to the Fantastic Garden)
Sung by Hatsune Miku with Megurine Luka With no control over the Fantastic Garden, Feather Pen Girl can only watch as it warps itself into something else.
 * Nicovideo Broadcast
 * Youtube Broadcast

ANTI THE∞HOLiC (Anti the Infinite Holic)
Sung by Kagamine Rin and Magurine Luka Two girls, Rho and Lambda, consider the various possibilities and outcomes that come with changing the future. The one they seek is a "concurrent light (ray)" that goes through the past, future, and present. An "Ideal Solution" will be met after escaping the closed circle of the "Forgotten World."
 * Nicovideo Broadcast
 * Youtube Broadcast (with Subtitles)

廃都アトリエスタにて (In the Ruined City, Atelestia)
Sung by Kagamine Rin & Len Two lovers head into the abandoned city Atelestia to pledge their everlasting love at the city's clock tower - a wonderful charm that's continued for hundreds of years. As they climb the clock tower, it begins to snow, and it "even changes the city that settled into sleep into a theater." Though there's no one else in the city, the clock still tolls the hour, as if giving the two its blessing.
 * Nicovideo Broadcast
 * Youtube Broadcast (with Subtitles)