2005 [Weekly Bunshun Mystery Top 10] #1
2006 134th Naoki Prize winner, 1st place in [Authentic Mystery Grand Prize], 1st place in [This Mystery is Amazing]
It was made into a film in Japan in 2008 (starring Masaharu Fukuyama).
3rd highest box office revenue among Japanese films released that year)
English version published in the United States in 2011 (The Devotion of Suspect X)
Made into a film in Korea in 2012 (starring Ryu Seung-beom and Lee Yo-won)
Filmed in China in 2017

A middle-aged man is murdered by a mother and daughter in a townhouse near Edogawa, Tokyo.
The dead man was the woman's second divorced husband, Dogashi.
A mother and daughter accidentally strangled and killed a man who came to extort money and was violent.
The woman's name is Yasuko Hanaoka.
She was once a bar hostess, but now works at a lunchbox shop and raises her daughter Misato from her first husband.
Ishigami, a high school math teacher who lives next door and happens to notice the incident, offers to help her.
Yasuko, who is in a corner, accepts his offer, and Ishigami, who has been deeply in love with Yasuko for a long time, sets out to create the perfect crime.
During his college days, he was known as a genius who only comes once in a hundred years. He created a flawless alibi and gave detailed instructions to the mother and daughter on how to respond to police interrogation, confusing the police investigation.


The day after the incident, the body of an unrecognizable middle-aged man is found, and the police determine that it is Togashi's body.
The investigation reveals that Togashi had been tracking Yasuko's whereabouts just before her death and had found out the address of the lunchbox shop where Yasuko worked.
Naturally, Yasuko emerges as a strong suspect in the investigation.
The police are working hard to verify her alibi, but they are not making much progress, and the investigation is at a standstill.


With the investigation at a standstill, detective Kusunagi sends an SOS to his college classmate Yukawa.
Yukawa, a professor at Deito University, is a genius physicist, aka "Detective Galileo," who appears whenever Kusunagi is in trouble and provides clues to solving the case.
Yukawa, who started to investigate the case, hears from Kusunagi the name of Ishigami, Yasuko's neighbor, and remembers that he was a classmate from their college days, with whom they had recognized each other's genius, even though their majors were different.
And I have a feeling that Ishigami is involved in the incident.


The case enters a new phase, and a fierce battle of wits unfolds between geniuses who cannot back down an inch.
However, at some point, Yugawa discovers his friend Ishigami's secret and falls into deep pity and worry.
I learned of Ishigami's devotion to a woman he loved so deeply and was willing to sacrifice everything to protect her.


How could a mother and daughter have such pretty eyes?
Until then, he had never been captivated or moved by anything beautiful.
I didn't even know the meaning of art.
But at that moment, I understood everything.
It was essentially no different from the beauty felt when solving a math problem. (Page 437)

The moment Ishigami sees Yasuko, who moved into the neighborhood and came to visit to say hello, he is captivated by her.
He was known as a genius mathematician in his youth, but after repeated failures, he now lives a single-minded life as a high school math teacher, wrestling with difficult mathematical problems alone. He found meaning and purpose in her.
For the Japanese, devotion is a kind of spiritual struggle to find the truth lost in a corrupt and decadent society.
There is no need for logic or reason here.
The only thing that matters is the purity of motive.
For this, he endures everything and ultimately even dies.
In a massive, tightly controlled society, the only actions an individual can choose purely are love and death.
That is why the double suicide of lovers who cannot get along with the world appears frequently in Japanese literature.


I had absolutely no desire to be with them.
I thought I shouldn't reach out to them.
At the same time he realized.
That math is the same.
Just being involved in something sublime makes me happy.
Seeking fame is a detriment to one's dignity. (Main text, pp. 437-438)

Feeling pressured by Yugawa's growing closer to the truth of the case, Ishigami eventually turns himself in to the police, claiming to be the murderer.
And he claims that he was Yasuko's secret bodyguard.
The police accept Ishigami as the culprit because the evidence he presented matches exactly with the results of the investigation so far.
Before turning himself in, Ishigami leaves Yasuko with some final words of advice.

Mr. Kuniaki Kudo seems like a sincere and trustworthy person.
If you combine with him, there is a high chance that you and Misato will be happy.
Please forget all about me.
You should never feel guilty.
Because if you don't become happy, all my actions will be in vain.

And finally, an unexpected twist awaits readers.
As if posing a math problem, Ishigami finally tries to put an end to the creation of the perfect crime by pointing out “the blind spots that arise from prejudice.”
However, Yugawa, who already knows the whole truth and is suffering from friendship and pity for his friend, tells Detective Kusunagi about Ishigami's trick with a heavy heart.
It was a story that no one could have imagined or believed, a story of immense dedication conceived and orchestrated by a genius mathematician to protect a mother and daughter from all the evils of society.


If he doesn't let you know that he loves you so much that he's risked his entire life for you, then it's not worth it.
He doesn't want this to happen, but I can't stand you not knowing anything.