The hero, Sam, is a 42 years old divorced ex-cop and the owner of a not very successeful detective agency. And dirty refers not to his mind or his line of work, but to the personal hygiene of our hero. The angel in the title his detective agency, named to catch customers' eyes when they leaf through yellow page. 

Apparently, the gimick works, because one day a boy came to the agency, claiming to be running from an assassin. At first Sam did not take him seriously, but he was convinced after a drive-by shoting that almost ended both their lives.  Leo is a young computer wizard who wandered onto a presidential assasination plot accidentally, and now it's up to the two of them to prevent the plot from being carried up. 

Thus begin the tentative friendship between Sam and Leo. As in most of Yoshimi Ozaki's stories, the plot is neglegible.  The relationship between Sam and Leo  is what drives the story.  There are some predictable elements. Leo the child wonder saving the president, teaching Sam about computer and internet, while Sam gave Leo his first lesson in shaving with a brush and razor, but Ozaki Sensei never allow the relationship to degenerate into banal sentimentality. In between Christmas presents and pets, she turns stereotypes on their heads, wrecks havoc with the traditional uke and seme dynamics, and make sly comments about generation gaps. "I'm Bruce, you're Robin," Leo told Sam as he gave bullied Sam into a tuxedo and gave him the invitation to a cocktail party. 

The author wrote in the afterwords: "Sam must be the oldest hero to grace the cover of Hanaoto.   I based him on our editor, who has been wonderfully supportive and clueless through it all."

Ozaki Sensei's off-beat sense of humor is in full evidence here, as she gleefully presents us with a dream wedding scene with Sam as the blushing bride, in all his five'o clock shadow and hirshute glory. 

Sometime touching, often hilarious, never predictable, this is probably Yoshimi Ozaki's best book, and certainly my favorite.