Rakko Yumiya (弓箭猟虎 Yumiya Rakko) is a character introduced in Toaru Kagaku no Railgun. She's a student at Private Shidarezakura Academy and serves as an antagonist for the Dream Ranker Arc and is an operative of SCHOOL.
Her surname Yumiya literally means "bow and arrow" and the given name Rakko as a whole, means "Sea Otter" in Japanese; if interperated separately, these two kanji literally mean "hunting" and "tiger" (although the Japanese for "hunting the tiger" is not written and read as such).
Rakko appears as an average-hieght teenage girl with long dark-colored hair with two pigtails in the back. She usually wears a schoolgirl uniform and on missions, she wears the same uniform but with a pouch belt.
At first glance, Rakko looks like an average highschool girl with a tone that appears to be rather shy and easily flustered to the point of dreaming of being popular and often stutters a lot. This is a stark contrast to her demeanor during missions where she's revealed to be very cold and ruthless. She takes pleasure in taking down her targets and often acts very sadistic.