His actions are always enigmatic, making it difficult to understand.

I wonder what this bento's mystery meat is made from.

This is the most difficult case I have ever faced.

The police said he is a ruthless murderer.

He was being pursued by the police as a lust murderer.

This case is highly likely to be a staged murder.

He got involved in a love affair.

The Asian giant hornet is a very dangerous insect.

The Tiananmen Square incident is an important event in Chinese history.

The Marco Polo Bridge Incident was the trigger for the Sino-Japanese War.