From what I can tell, the official translation (or at least an agreed upon translation) is “A returner’s magic should be special”. So here’s the breakdown with my personal translation!
귀환자 is defined as “a person who leaves a place and returns back to where they’re originally from”
-> In English, this is a “returnee” but they translate it as “retuner” which also makes sense because the character was sent back 13 years into the past.
–> From what I found on google, “returner” is defined as a person who returns to work after a break while “returnee” is a person who returns to a place after a prolonged absence.
-> Technically, he returned to a time period…. A time period where he was enrolling in the most prestigious university of magic (Hevrion 헤브리온)
-> This is fairytale magic. Real world magicians use 마술 and are called 마술사 while fairytale magicians are called 마법사
특별하다 to be special
-> As an adjective it’s 특별한… 특별한 마법 a special magic.
해야 하다 need to / have to / should / must
-> when you want to say that you need/have/should do something, you can use 해야 되다 or 해야 하다. So in this case “must” as in “needs to (be)”. You use the informal conjugation of the verb + 야 하다/되다.
–> I should do my homework 숙제 해야 해요
–> I have to work this weekend 이번 주말에 일해야 해요
A returnee’s magic must be special
As you can see, there’s all kinds of ways you can translate this, but all would mean he returned somewhere (or to something) and has special magic 🙂