Step 2: Get the main pairing together while preventing the MomoKai
Step 3: Reinforce that the main pairing is in True Love Forever and there is NO MomoKai
Step 4: Brace for the inevitable "Loved the Sekrit MomoKai!" comments
It's that difficult, seriously. I give them boyfriends, I give them girlfriends, but to no avail. All they have to do is stand next to each other and the sparks fly and fly.
If Momo and An were celebrating their 50th wedding anniversary and Kaidoh and Inui were attending, having been together themselves for at least that long, and Kaidoh was the most faithful and loving and true partner of all time, and Momo was suffering from erectile disfunction, and everyone was raptly watching the cute little grandchildren sing a cute little song about how much they loved their grandparents, An would definitely have her eye on Momo and Inui would grab Kaidoh's arm very tightly because they would STILL be five seconds away from snarky sex in the bathroom.