They have a similar feel, of course Japanese and Korean culture- though similar in some ways, are quite different. And of course the main character in IL plays 'Go' and in March he plays 'Shogi.

Not as dark/psychological as oldboy but, if you've seen oldboy you'll definitely get 'oldboy vibes' from this film. They're both thrillers. I won't say anymore because I feel it would ruin the experience, definitely a film you should go into without knowing anything.