As well as her manga series, Touma Kaori also illustrates the Cobalt novel series Tokyo S Kibi Tanteidan, which is written by Hibikino Kana. It has 9 volumes out now.  It's about a detective agency with uncommon high school students.  I read the first one for a Japanese project, and it was hard.  I have up to Volume 7, but it's going to be a long time before I try reading another one.