Mc is just a high schooler, and probably used to being on his own and spends too much time in a hospital during his childhood days, and there's no signs of MC having any relationship experiences beforehand. He's not expected to be a genius in how a relationship works.
Kid just needs to practice on his communication skills. The lack of actual parental relationship and guidance ain't helping MC either
I'm confused who's the main couple or second couple?
Short answer, there is no main couple. Both couples are shown equally romantic wise. Just Kinard has the most knowledge over the whole situations so we see him more in the beginning/ important parts. From what I've read in interviews with the creator all four characters are important to the story. His relationship with Lou is what fuels a lot of the plot. If the creator had to chose an MC it would lean closer to Kinard.
Mukoda is legit male wife.