The love triangle and the beginning of problems

I feel like Sol is being too hard with himself. He obviously likes Piano but he knows that Sun likes her too. I like Sol and Piano together, they are so adorable. I also feel bad for Sun but there is really no need for him to compete against Sol. Also, Sun is same age as Sol so I feel like he should be aware of the household problems but I guess it adds up to his personality in the series. I know the Korean version but I'll be tuning in if there are changes.