Story
You play the role of Azai Kyosuke, the adopted son of a legendary gangster infamous in the underworld. You spend your time listening to Bach, playing God at school and covertly working for your adoptive father as a ruthless financial heavyweight. This idyllic existence is broken when two individuals appear in the city - a beautiful girl named Usami Haru, with hair you could get lost in for days, and a powerful international gangster known only as Maou. Almost without delay, the two begin a deadly cat-and-mouse game, bringing you and your friends into the crossfire. Plotting, political intrigue and layer upon layer of interlocking traps are the weapons in this epic battle of wits.

Note: The title is a reference to "Air on the G String" - a famous classical music piece.
Taken from VNDB