Three Assassins: Kotaro Isaka

Suzuki is just an ordinary maths teacher...until his wife is murdered.
Seeking justice, he leaves his old life behind to infiltrate the criminal gang responsible. What he doesn't realise is that he's about to get drawn into a web of the most unusual professional assassins, each with their own agenda:
The Whale convinces his victims to take their own lives using just his words.
The Cicada is a talkative and deadly knife expert.
The Pusher dispatches his targets in deadly traffic 'accidents'.
Suzuki must take on the three assassins to avenge his wife - but can he keep his innocence in a world of seasoned killers?
Their mission is murder. His is revenge.