The simplest way to say 'I love you' in Korean (or 'You love me,' 'I love you,' etc., since Korean doesn't use many pronouns like Vietnamese) is 'saranghae.' However, there are several other expressions that you can use to convey your feelings. Below are some phrases you should know.
Steps
Direct ways to say 'I love you'

Say 'saranghae' or 'saranghaeyo' or 'saranghamnida.' Use these phrases to say 'I love you' in Korean.
- The pronunciation of this phrase is sa-rang-he-yô.
- In Hangul, 'saranghae' is written as 사랑해 and 'saranghaeyo' is written as 사랑해요.
- 'Saranghae' is a natural way to say 'I love you,' 'saranghaeyo' is a polite way to express the same feeling, and 'saranghamnida' is the most formal way to say it.

Say 'nee-ga jo-ah.' Use this phrase to say 'I like you' in a romantic context.
- The pronunciation of this phrase is nè-ga giô-a.
- To write this phrase in Hangul, it is written as 네가 좋아.
- This phrase means 'I like you.' It is an informal expression used in romantic situations.

For a more formal version, say 'dang-shin-ee jo-ah-yo.' This phrase should also be used to say 'I like you' in a romantic way.
- The pronunciation of this phrase is dang-shin-i giô-a-yô.
- In Hangul, it is written as 당신이 좋아요.
- This phrase also means 'I like you,' but it shows a higher level of respect and formality. It should also be used in romantic contexts.
Other ways to express love

Affirm as follows: 'dang-shin-upsshi motsal-ah-yo.' This is a formal expression indicating that you cannot live without the person.
- The pronunciation of this phrase is dang-shin-óp-si mốt sa-la-yô
- In a relatively literal translation, this phrase means 'I can't live without you.'
- In Hangul, it is written as 당신없이 못 살아요.
- A more natural way to say this would be 'nuh-upsshi motsarah,' or 너없이 못살아.

Let someone special know 'nuh-bak-eh upss-uh.' Use this phrase to tell someone they are unique and irreplaceable.
- This phrase is pronounced as no bắc-kê ọp-so.
- The rough translation of this phrase would be: 'There is no one like you.'
- To write this in Hangul, it is 너밖에 없어.
- A more formal version of this sentiment is 'dang-shin-bak-eh upss-uh-yo,' or 당신밖에 없어요.

Say with confidence 'gatchi itgo shipuh.' This simple phrase will let the other person know that you're interested in developing a romantic relationship with them.
- The pronunciation of this phrase is ga-chi ít-gô-síp-po.
- A fairly literal translation of this phrase is 'I want to be with you.'
- This phrase is written in Hangul as 같이 있고 싶어.
- To make the phrase more formal, say: 'gatchi itgo shipuhyo,' or 같이 있고 싶어요.

Ask someone out with the question 'na-rang sa-gweel-lae?' This is the perfect question to ask if you're hoping to start a relationship with someone.
- The pronunciation of this phrase is na-rang sa-quy-lế.
- A literal translation of this phrase is 'Do you want to go out with me?'
- This phrase is written in Hangul as 나랑 사귈래?.
- To ask this question more formally, say 'juh-rang sa-gweel-lae-yo?' or 저랑 사귈래요?.

Propose with the question 'na-rang gyul-hon-hae joo-lae?' If your relationship is serious enough and you're ready to take the next step, this is the question you'll want to ask.
- The pronunciation of this phrase is na-rang kyol-hôn he ju-lế.
- This phrase translates roughly to 'Will you marry me?'
- The Hangul version of this phrase is 나랑 결혼해 줄래?.
- A more formal way to ask this would be 'jeo-rang gyul-hon-hae joo-lae-yo?' or 저랑 결혼해 줄래요?.
Related phrases

Tell them 'bo-go-shi-peo-yo.' This phrase is used to tell someone that you miss them.
- The pronunciation of this phrase is bô-gô síp-po-yô.
- A direct translation of this would be 'I want to see you.'
- The Hangul version of this phrase is 보고 싶어요.
- A more natural way to express this feeling is to omit the 'yo' or 요 at the end of the phrase.

Let a girl know 'ah-reum-da-wo.' This is a wonderful way to compliment a girl or woman you like.
- The pronunciation of this phrase is a-rưm-đa-ua.
- The literal meaning of the phrase is 'You are beautiful.'
- This phrase is written in Hangul as 아름다워.

Let a guy know 'neun-jal saeng-gingeoya.' This is a great way to compliment a guy you admire.
- The pronunciation of this phrase is non-jal seng-kin co-ya.
- This phrase literally means 'You are handsome.'
- The phrase is written in Hangul as 넌 잘 생긴 거야.

Playfully say 'Choo-wo, ahn-ah-jwo!' Use this phrase when you want to ask someone you love for a hug.
- The pronunciation of this phrase is chu-ua an-a-chùa.
- A more literal translation of this phrase is 'It's so cold. Hug me!'
- 'Choo-wo' means 'It's so cold.'
- 'Ahn-ah-jwo!' means 'Hug me!'
- This phrase is written in Hangul as 추워. 안아줘!.

Keep someone with you by saying 'narang gatchi eessuh.' This phrase should be used when you want to keep someone from going home or leaving after a romantic evening.
- The literal translation of this phrase is 'Stay with me.'
- This phrase is written in Hangul as 나랑 같이 있어.