In the near future, Bond Creatures called "Mushi", insects, exist. They grant power to their host, but at the cost of the host's dreams. A war rages between the Mushibane, a group of Mushi hosts who fight for freedom, and the Special Environmental Conservation Executive Bureau (SECB), who seek to maintain The Masquerade. In the midst of this war, Daisuke "Kakkou" Kusuriya, one of the SECB, meets with a girl named Shiika for the second time. They grow closer as the war continues.
Based on a series of Light Novels. A sister series of audio dramas, Mushi-Uta bug, was included with the limited edition DVDs. The book was adapted into an anime in 2007 by Beat Frog.
This work provides examples of:
- Arc Words: "What is your dream?"
- Arm Cannon: The fully powered version of Daisuke's Mushi turns his entire arm into a blaster.
- Bond Creatures: The Mushi
- Code Name: Members on both sides of the battle take on the name of their insect as a code name. The search for "Fuyuhotaru" is central to the plot.
- Double Agent: Minmin.
- I Want My Beloved to Be Happy: Rina, in response to Shiika.
- Incredibly Obvious Bug: In more ways than one. Minmin's power is to use insects for spying.
- Inside a Computer System: Asami's power manifests itself as this.
- Invincible Hero: It is explicitly stated that being the cockroach makes Daisuke the most powerful host ever known. Although, being invincible in combat doesn't prevent him from failing missions, nor all the bad things happening to him.
- La Résistance: The Mushibane.
- Love Martyr: Minmin.
- Love Triangle
- The Masquerade
- The Men in Black: SECB.
- Mysterious Waif: Shiika.
- Our Souls Are Different: One's Mushi is tied to one's dreams/soul, and if a person's Mushi is killed, they get Laser-Guided Amnesia and become The Heartless. It is possible to regain their dreams, though.
- Post-Episode Trailer: Playing off the Arc Words, each member of the cast describes their own dreams and tells the next episode's title. No actual content about the next episode included.
- Snow Means Death: Shiika ("Fuyuhotaru") invokes this trope in her battles.
- Technopath: C and Asami stand out the most.
- Those Two Guys: Rina's three friends, one of whom (Asami) becomes important.
- Triple Shifter: Rina, as both the leader of the Mushibane and a normal high school student.