Piranha

A worker who cuts sheet metal in a plant loses his arm so that his spouse can use the million-yen payout to open her own club. Spending his days idly, he purchases a tank of piranhas. One day, after spotting her outside a hotel with another man and getting criticized by her, he submerges her wrist in the tank and she is bitten. She leaves him and he returns to work at another sheet metal plant.

(Source: Wikipedia)