An Affair (2008)

Sakurai is a pretty police office lady working in Roppongi Police Station. Instead of a challenging environment, her daily work is simple and rather boring though she belongs to the Serious Crime Detection Section. A homicide case in Roppongi turns the brother of Sakurai's best friend into the murder suspect. Sakurai determines to spend her weekend to investigate the case herself to find out the true murderer. While she discover a mysterious website link to a large gang of criminals, her unexpected weekend begins...