This is the 265th most frequent Korean word.
라는
"라는" is a Korean particle used to indicate something called or referred to as.
'라는' introduces the quoted word or phrase '천재' to describe what was heard.
나는 그가 '천재'라는 말을 들었어요.
I heard that he is called a 'genius'.
'라는' is part of '진실이라는', which qualifies '것' (thing) to mean a defined concept, 'the thing called truth.
그는 '진실이라는 것은 중요하다'고 가르쳤다.
He taught that 'truth is important'.
'라는' introduces '전설' as the name of the cafe, giving the concept or title.