Mushihime-sama is an arcade bullet hell game developed by CAVE and distributed by Ami in 2004 for the CV1000 arcade board. The game was created in an attempt to stray from the "bullet hell" genre and return to a difficulty level they would describe as "more Toaplan"; that is, to appeal to a more casual audience.
Something rather unique about Mushihime-sama compared to other shmup titles of the time (especially from CAVE) was the avoidance of common tropes in the genre. Though the project originally started as yet another militaristic tanks-and-planes shmup, rumors of a new Raiden game on the horizon (what would become Raiden III) caused CAVE to reconsider the direction of their project. CAVE decided they wanted to stray from the norms of the military or sci-fi shooting game and instead concerned Mushihime-sama entirely with the diverse pallete of nature.
Koujuu (carapace beasts) are the dominant species in the land of Mushihime-sama. It's implied that few creatures are able to live outside of the relatively tame forests and within the sprawling desert, intense volcanic kraggs, and intricate underwater cave systems. The Koujuu way of life is upheld by "Levitation Energy", allowing them flight and the ability to fire purple energy-based projectiles. The mere energy that Koujuu emit is poisonous to humans, forcing them to the top of the food chain. Humans begged the Koujuu God for a safehaven for the remaining scraps of their civilization to live, and they were blessed with Hoshifuri Village within the Shinju Forest. In return, every 200 years the humans must sacrifice someone on what would be their 15th birthday. Princess Reco, the protagonist and player character, is next in line to be sacrificed, but the village refuses to offer her up. In retaliation to the human's selfish acts, the Koujuu god plagues the village with the Miasma. Reco (and her bug companion Kiniro) set out to confront the Koujuu God and stop his tyranny.