Did you know?

1. The correct English title is "Dear Haeri" or "To My Haeri" or "My Dear Haeri"?
2. The character's name is "Haeri" and not "Hyeri"?

Details

1. Korean title: 나의 해리에게 (naeui haeriege)
2. Dissociative Identity Disorder: 해리성 정체성 장애 (haeriseong jeongcheseong jangae)

The artistic connections you are missing by using the incorrect "Hyeri"

1. The name of the character, "Haeri" is in the show's title.
2. The name of the character, "Haeri" is in the Korean translation of DID.
3. The character is a second personality of Eunho.
4. Eunho will more likely start to struggle with Haeri and attempt to communicate with her, and possibly learn to appreciate her as well. Hence, "나의 해리에게" (Dear Haeri).

It's a play on words, and it is artistic. It is a disservice to the author's artistic creativity to rename the character as "Hyeri" and to use "Dear Hyeri". It, "Hyeri", is also completely disconnected from the author's work.

What happened?

1. Someone (North American OTT service more likely) made a mistake in transliterating the character name and title to "Hyeri". They more likely have a small font so they got confused.
2. Everyone else copied the wrong title without doing their due diligence.
3. To add fuel to misinformation, fan-made "English" posters started to show up and used in various databases.
4. The incorrect English title and posters reached the Korean producers, and they started using it as well. (We can't blame them, English is not their strong suit, and they generally don't care about the Romanization of Korean. They more likely just assumed what they saw as the "English" title and posters are correct.)

If you think that was it…

1. Fans were already talking about the show for months. They all got it correctly as "Haeri".
2. Online translations, most especially Naver Papago, all Romanized it as "Haeri".
3. "Hyeri" is harder for non-Asians to pronounce than "Haeri".

Artistic license?

Because "Haeri" is hard to pronounce so they replaced it with an even harder "Hyeri"?

It doesn't makes any sense, right? Let's say both are equally hard to pronounce. If they'll use the "artistic license" reasoning, why did they not come up with "Dear Hailee"? You know, Haeri -> Haeli -> Hailee. Don't tell me "Hailee Steinfeld"'s name is harder to pronounce than "Haeri" and "Hyeri"!

Oh. Hey, if you haven't noticed it yet, the name of the character being "Haeri" adds a depth to the story and the character. Did you see the connection of her name being "Haeri" as explained earlier? It doesn't exist in "Hyeri".

I know who Haeri is, but who is Hyeri?

The nail

1. 해리 = haeri
2. 혜리 = hyeri
3. 나의 해리에게 = naeui haeriege
4. 나의 혜리에게 = naeui hyeriege
5. 해리성 정체성 장애 = haeriseong jeongcheseong jangae (Dissociative Identity Disorder)
6. 혜리성 정체성 장애 = hyeriseong jeongcheseong jangae (Hyerythrotic Identity Disorder)

Anyone knows what "Hyerythrotic Identity Disorder" is?

Now you know!