The EAI attributes the rise to worsening ties between the two countries, rising tension and military clashes in the Korean peninsula over the last decade that resulted in South Korean casualties.
In 2005, during the era of rapprochement between the Koreas under President Roh Moo-hyun's administration, the number of South Koreans who viewed the North as an enemy was 15.3 percent.
Relations cooled under the administration of conservative President Lee Myung-bak and in 2010, the year North Korea bombed the South Korean island of Yeonpyeong and Seoul accused Pyongyang of sinking one of its warships (two incidents which left 50 South Koreans dead), the figure climbed to 31.9 percent.
According to the EAI, a series of successive incidents such as the alleged placement of landmines by North Korea, which seriously injured South Korean soldiers, have only served to further damage the image of North Korea among South Koreans.
The number of South Koreans who view North Koreans as brothers has fallen from 52.1 percent in 2005 to 42 percent in 2015.
The survey also shows the number of South Koreans, who do not view the reunification of the two countries as beneficial, rose between 2014 and 2015 and South Koreans across all age groups surveyed showed growing mistrust towards a Korean reunification project, especially young people, 32.4 percent of whom favored a unified Korea, 28 percent less than in 2014.
North and South Korea are technically still at war as the armistice that ended the Korean War in 1953 was never replaced by a definitive peace treaty.