スウィートブラッド

From Storm in Heaven:

Possessing extraordinary detective skills and even helping out at the police department can't be normal, and anyone who knows Uryuu Nanao knows that she's different from the rest. It is this distinctiveness that draws both Karasuma Nozomi and Sakuragawa Nozomi to her despite Nanao's attempts to distance herself from them both. However, a series of murders take place and Nanao is forced to enlist their help in order to unravel the truth behind her father's murder. Just who is the real mastermind behind the ongoing murders and why are they targeting Nanao? And what is the secret left behind by Nanao's father?