It seems to me that women dating Korean men attribute most of their relationship problems to the ethnicity of their partners. It's as if we Korean guys have so much baggage related to our motherland that it's impossible to overcome the obstacles imposed by our Korean blood. Well, I have news for you, ladies. It's not that simple.
The Korean wrote a
very nice piece about it and it's worth reading to any girl out there trying to keep her Korean boyfriend or husband. You will notice he emphasizes the point that Korean men are not that much different from any other type of men and that we are men before we are Koreans. I second that, just adding that we Korean men are way hotter and better in bed than anybody else. "Me love you long time" is something that should be said by Korean men and not Asian hookers, at least that's what the girls who had the joy of sleeping with one of us keep telling me. "Once you have kimchi", they add, "you will always want more kimchi". "That's kinda lame...", I complain and then they just mention something about not being polite to talk with their mouths full and keep doing what they were doing.
Out of my characteristic generosity though, I have some additional words for those girls out there who are in relationships with Korean men.
We, like any other men, are selfish pricks who think mostly about sex. Whenever we meet your girl pals we will be mentally evaluating their bodies and giving them grades between fuckable and unfuckable. We will also be fantasizing about a threesome, involving us and two of your hottest friends, maybe with you filming it and giving them tips on how to please us best.
We're insecure, so any male friend of yours will be seen as a potential competitor. And please, please, if you've slept with more than two guys before you met us, please lie about it and say it was only one. And don't forget to mention how much better we are in bed.
We're liars too so don't go looking for a ruler when we mention something about six inches. The distance between the tip of the thumb and the tip of the index finger should perfectly illustrate what six inches are.

We like sports, so please try to keep the noise to a minimum while we're watching TV. If you have to use the vacuum cleaner in the room where the TV set is, please do it after we're done with it and taking a nap after all those beers you
silently brought us from the kitchen.
Now, with all joking aside, some serious advice:
Be aware that Korean guys are way more serious about being Korean than our sisters. I believe Korean women have more courage and therefore they may date and fall in love with non-Korean men more easily. But for us it's a lot more difficult to be thrown in such a cultural mix. If you feel (even slightly) that he's a little reluctant in being seen with you in public places (specially those in which other Koreans are likely to be present) do confront him right away. He may not be ready for a serious relationship.
If he's introduced you to his Korean friends and family, that's a better sign. But don't stand still. Try to get to know more of his friends and family. The better your relationship with those people is, the better your relationship with your partner will be.
And for last, his mother. Don't be afraid of his mother. Remember she's like a pitbull terrier, her reputation and barks are way worse than the reality. Come on, who would be scared of the woman below?

Remember it's likely she went through a lot of hard work to raise your man and therefore she rightly demands some well earned respect. She won't be easy to deal with at all. Korean women (specially your man's mother) have this incredible ability to say stuff that can be very hurtful if you take it the wrong way. But if you wanna do the crime (take this man away from her) you will have to do the time. Some people may advise you to learn some Korean (in the case she doesn't speak your language) or that you should show nothing but respect for her. I call shenanigans on that.
First, the language thing. If you live in Korea then yes, maybe it would be wise to learn some Korean, even if you're not dating a local man. But how in the hell should you learn such a difficult language if you don't live in that country? It's very easy to learn how to read hangul, you can do that in one day. But what good is reading if you don't know what that sound means? So, fuck that. Forget about learning Korean and concentrate on other things.
Second, the respect. You should respect your man's mother (and everybody else in his family) but please don't fall in the trap of becoming her little pet. If you agree with everything she wants or demands she will have no respect whatsoever for you. Show your respect for sure (respect for older people is an extremely important part of Korean culture) but establish some limits. If you say yes to everything then you're doomed. Don't be a kiss ass.
Instead, try to develop your own relationship with her. Treat her with respect but as an equal. Listen respectfully to her advices, consider them seriously. But if you disagree with some points you should definitely make it clear what your opinions are.
I know she will want to be a meaningful part in your life as a couple so allow her to do that. Invite her over for dinner, ask her to go shopping with you, cook for her and with her. Talk to her about her son, ask questions about her experiences. No, it's not easy, but in the end she's a woman just like you. She will understand.
The worst thing to do regarding your potential Korean mother in law is to internalize your feelings. If you keep everything inside you will go crazy. Complaining to your Korean man won't help much because Korean men are very sensitive when it comes to their mothers. It's got nothing to do with his love for you. He will probably try to explain his mother's point of view and we all know that will be disastrous.
So if you have something to say, say it to her. Very respectfully, of course, but do it. With time, things will get easier. Specially if you follow my advice and become her friend.