Why kai don't marry me?

Answer from: DariDari~
You need to finish all the heart events before you can marry him. Don't worry about the green or orange heart events cause there are none.

Black Heart Event - Go to Mineral Beach on a Monday, Wednesday, or Friday between 11:00 am - 1:00 pm or 5:00 pm - 7:00 pm. You 2 will start talking, then Kai will ask if its bad to be a person who doesn't like his family.
Pick option 2.

Purple Heart Event - Walk into Kai's restaurant on a Monday, Wednesday, or Friday when he is inside. He will ask if you're growing any crops on your farm.
You have 1 of 3 options to tell him, 1st one is 'pinkcat flowers", 2nd is "alot of pineapples" & the 3rd is "nothing yet". Pick the 2nd one, "alot of pineapples".

Blue Heart Event - You have to have your strength down to 50%. Or, what I'm guessing is, you have to work really hard to the point to where your face is blue.
Visit the beach on a Tuesday or Friday between 1:00 pm - 5:00 pm. As you walk up to him, you will pass out & he'll take you to the clinic.
At the clinic, Kai suggests that you take it easy with your work.
Pick option 1, that he might be right.

Yellow Heart Event - Go to the beach on a Monday, Wednesday, Thursday, or Saturday between 9:00 am - 11:00 am. You'll find Kai at the dock. He hasn't been getting alot of customers & he then asks what you think of him. He says he feels as if the other boys in town think he is a jerk because he refuses to act "fake". He wants to know if he should change his ways.
Pick option 1.