Kohakuiro no Namida

Max and his wife worked at police. But 10 years ago his wife got killed during a police operation and Max has led repeated, alcohol-dependent life ever since. One winter day at the dusk he and general store owner Koharu find a mysterious girl Mil in metal collar and shackles. Koharu persuades Max to give the girl shelter just for one night and Mil stays to live with him. Max falls in love with Mill and decides to protect her instead of his deceased wife that he could not protect.

[From vndbreview]