Aria the Scarlet Ammo

A young girl idolizes the world-renowned S-ranked butei Kanzaki H. Aria and plans to follow in her footsteps. However, her test grades her out as only an E-rank! All is not lost, however, as Aria agrees to give her some pointers. Can Aria help this newcomer become a first-rate butei?

The story takes place in Tokyo Butei High School, a special school where armed detectives — "Butei" — are trained to use weapons. Kinji Tooyama is a second-year-student who has a special ability, but he keeps it a secret to maintain an ordinary, peaceful life. However, when he gets caught in a bombing on the way to school, he encounters H. Aria Kanzaki, the most powerful S-Rank Butei student in Assault Studies.

Akari Mizunashi dreams of life after attaining her goal of becoming a Prima Undine, but upon waking realizes that she might not actually have the confidence to run Aria Company on her own. Wary of the future, she seeks advice from her mentor Alicia Florence—one of the three great "Water Fairies" of Neo-Venezia. Much to Akari's surprise, Alicia reveals her own struggles of the past, but also shares the steps she took in overcoming her self-doubt of running the company and taking on an apprentice. Finding solace in her teacher's words, Akari prepares to embrace whatever trials she must overcome on her path toward achieving her dreams.

In Neo Venezia, Akari, Aika, and Alice continue to work diligently toward the day they become full-fledged Prima Undine (a professional tour guide gondolier). The girls have come far since they began their training, and they are slowly forming their own distinctive styles as tour guides for the city. On the long journey towards their goal, the girls have relied on the advice of their seniors from their respective companies: the patient and understanding Alicia from Aria Company, the strict and proper Akira from Himeya Company, and the clumsy yet caring Athena from Orange Planet Company. Will the girls be able to blend the advice from their mentors with their personally acquired knowledge of Neo Venezia to become praiseworthy Prima Undines? Welcome once more to Neo Venezia; the city that personifies warmth and tranquility.