Cognomen トウナイ (Tonai 
, トウナイ ) , in the entire world, is a rare surname. The family name トウナイ is characteristic of Croatia, where it is a rare surname, Hungary, and Singapore, where it is a very rare surname. In absolute terms, it is commonest in India, the United States, and Hungary. More prevalently, トウナイ is the forename as well as the last name.