FAKE Vol 3

Ryo and Dee are on the hunt for a serial killer who murders women who look like prostitutes. They're aided by FBI agent Diana Spacey, a brilliant investigator who is an old friend of Berkeley's. Soon, she is caught in the serial killer's web, and it's up to Berkeley and the gang to save her. In the second act of the story, Ryo's childhood is explored. It's revealed that Ryo's parents died when he was young and that he was raised by his aunt. It's the Christmas season, and Ryo doesn't want to spend it alone. On Christmas Eve, Dee comes to wish him a "Merry Christmas" and Ryo is extremely touched by the sentiment. All of their fiery feelings finally lead to one, hot kiss.

Source: Anime News Network Encyclopedia