Suugaku Joshi Gakuen (2012)

Both series are Female Centered Plot which focuses on competition in winning particular game or activities. Suugaku Joshi Gakuen is about girls who competes in Math and Girl Gun Lady is all about winning in the fight which is a survival game. If a competitor lose it would subtract their life span.

Both protagonists are female mathematicians who uses their knowledge to solve problems. Hard Nut is more of a detective, which is a little more intense, while Suugaku Joshi Gakuen is a school drama.