1. Use polite verb forms.
Basically, Korean has two types of verb endings for polite speech style: 요(yo) and 다(da). When writing fan letters to celebrities, 요(yo) form is more appropriate than 다(da) form; 다(da) would sound too polite and formal for that kind of letter.
2. Use polite noun forms.
In Korean, some nouns have entirely different forms for plain speech and honorific speech. To be polite, use 저(jeo) / 제(je) instead of 나(na) / 내(ne). 저(jeo) is the equivalent to ‘I, me’ in polite speech. 나(na) is the casual form of 저(jeo). 제(je) is the equivalent to ‘my’ in casual speech. 내(ne) is the casual form of 제(je).
3. But don’t be too formal and too polite.
I’ve noticed that a lot of Korean learners tend to use the most polite noun forms when writing. Erring on the side of politeness is, of course, always good and safe, but in this fan letter, too-formal and too-polite nouns would sound a little awkward to native speakers (that is, the celebrities who will read your letter).
Do not use 당신(dangshin). Instead, choose the right title for them, such as 오빠(oppa), 언니(unni), 누나(nuna), or 형(hyung), and use it.
4. Choose the perfect titles for celebrities.
If the people you’re sending a letter to are older than you, you should use an appropriate title for them. There are four kinds of titles you would use.
The most common titles are 오빠(oppa), 언니(unni), 누나(nuna), and 형(hyung).
But what if you would be the same age as he/she?
Adding the suffix씨 (ssi) to the name could be the appropriate solution in polite speech.
When writing the letter with casual speech, you would attach 아 to the name ending in a consonant or 야 to the name ending with a vowel.
In most cases, the given names are used with the titles we’ve just learned : First name + title.
(from a male/female who is the same age as Sehoon in polite speech)
(from a male/female who is the same age as Baekhyun in casual speech)
(from a male/female who is the same age as Suho in casual speech)
민호 오빠 Minho oppa
(from a female younger than Minho)
티파니 누나 Tiffany nuna
(from a male younger than Tiffany)
5. Attach 께 or 에게 to titles in the first sentence of a letter.
The Korean equivalent of “to / dear” is “께(kke)” or “에게(ege)”. Though grammatically 께(kke) is the more honorific form than 에게(ege), there is no big difference between them. Just choose whichever you’d like to use.
중기 오빠께 / 중기 오빠에게
To Joongki oppa, Dear Joongki oppa (from a female younger than Joongki)
Here is the entire example of a fan letter written in Korean.
This letter was written to 송중기 (Joongki Song, a male Korean actor) by a younger female fan. For reference, I've made some blanks.
You can freely adapt this template to suit your context, and fill in the blanks with the name of the celebrity you love!
To Joongki oppa,
안녕하세요. 저는 (싱가폴)에 살고 있는 (중기 오빠) 팬 (제시카)예요.
Hello, I’m your fan Jessica from Singapore.
(오빠)가 나오는 드라마 ‘(태양의 후예)’를 정말 재밌게 보고 있어요. (오빠)가 나온 영화 ‘(늑대소년)’도 봤어요. (오빠)는 정말 멋있어요. 제가 제일 좋아하는 (배우)예요.
I’ve enjoyed watching your drama ‘Descendants of the Sun.’ I also watched your movie ‘A Werewolf Boy.’ You’re so cool. You’re my favorite actor.
(어제) (오빠)가 큰 상을 받아서 정말 기뻤어요. (오빠)는 충분히 그 상을 받을 자격이 있어요.
I felt so happy as you won the big prize yesterday. You fully deserve it.
(다음 달)에 (홍콩)에서 팬미팅을 한다는 소식을 들었어요. (싱가폴)에서도 팬미팅을 했으면 좋겠어요.
I’ve heard that you have a fan meeting in Hong Kong. I hope you also hold it in Singapore.
(오빠)를 아직 한번도 만나지는 못했지만 제 사랑과 응원은 식지 않을 거예요.
Although we’ve never met, my love and support for you will never fade.
항상 건강하세요! 그리고 다음 (작품)도 기대할게요!
Always take care of your health! I’m looking forward to your next work!