Original Title: 生徒会探偵キリカ
Romanji: Seitokai Tantei Kirika
English Name (Translated): Student Council Detective Kirika
Author: Sugii Hikaru (杉井光)
Illustrator: Pon Kan (?) (ぽんかん)
Publisher: Kondansha (講談社)
Volumes out: 4 (as of June 2013)
From MangaUpdates:
Kirika Hijiribashi is the Executive Committee Treasurer managing a high school Student Council budget of 800 million yen. She is also the only committee member with an additional title: Student Council Detective able to sniff out amazing solutions to bizarre cases. Hikage Makimura, who recently transferred into the high school, finds himself not only tricked into joining the Student Council, but is now assigned as her assistant.