She appears in manga only, for the first time at chapter 147 (Vol. 18) of the series.
Makoto Fuyutsuki is Azusa's younger sister, she's 17 years old and is enrolled at the Nagaoka High School.
She's the founder of her school's Detective Club and is also Judo White Belt.
In the manga version, Azusa's background is more showed.. especially the part regarding her family.
Makoto pops in when Azusa has gone missing. Unfortunately for Teshigawara, he didn't calculate family involvement into his plans of Azusa domination. Things get interesting as the serie's version of Sherlock Holmes goes into action, with Onizuka tagging along as Watson. She is very smart and sneaky.. being able to unravel the mystery of Azusa's disappearance in such a great way.
She is hinted to have a great potential in a possible future as Detective, being able to solving the problem within one volume.