The Anime Lad
Kinji attends a school where young mercenaries train for dangerous work. Aria is its volatile top assault student. When she discovers the unusual condition that turns him into an exceptional fighter, she strong-arms him into becoming her partner. The recruitment process allows limited discussion from either student.
Gigguku
Kinji attends a school full of armed specialists and somehow still has the strangest secret there. Once Aria discovers his hidden combat talent, she decides they will work together. Her forceful confidence meets his awkward condition, giving their partnership immediate comic friction inside every dangerous assignment.
Father's Basement
The condition behind Kinji's ability is peak adolescent contrivance, and the premise has no intention of hiding that. The pairing around it is more useful. Aria is already an accomplished assault student, while Kinji's exceptional talent depends on a condition neither can treat casually. Their forced partnership makes every dangerous assignment personally awkward.