난 니가 볼 때마다 행복해 I'm using the informal language because this is directed to the person you're dating hehe 난 is the informal for "I" I'm sorry if there's any mistake, this is only based on my understanding (:

formal: (전) 당신을 볼 때마다 행복해요 informal: (난) 널 볼 때마다 행복해

난 널 볼 때마다 느낌이 참 행복해