Here's the catch though! He did stay single for 3 years and you know where he found himself after being single for that amount of time? Joowon all over again!!! No matter how you twist and turn Haesoo's feelings and their situation, it will never change the fact that he'll always go back to Joowon over and over. Also, Haesoo has become relaxed and playful with Joowon just like old times but Haesoo with Taku on the other hand? He always needs to be considerate and careful around Taku that he never got to truly act the way he wanted and perhaps, Haesoo just felt that he truly couldn't be himself if it's not with Joowon.
//spoiler
Here's the catch though! He did stay single for 3 years and you know where he found himself after being single for that amount of time? Joowon all over again!!! No matter how you twist and turn Haesoo's feelings and their situation, it will never change the fact that he'll always go back to Joowon over and over. Also, Haesoo has become relaxed and playful with Joowon just like old times but Haesoo with Taku on the other hand? He always needs to be considerate and careful around Taku that he never got to truly act the way he wanted and perhaps, Haesoo just felt that he truly couldn't be himself if it's not with Joowon.