。。
You're all I can see. I mean it.
Literal
I [of-の] eye [in-に-は] you only reflected-not [emphasis-よ]. Real [assertive-さ].
Two sentences. The first uses 映る ('to be reflected, to appear in [a mirror/image]'), here metaphorically — 'reflected in my eye' = 'seen by me.' The しか...ない pattern ('only, nothing but') combined with 映ってない gives 'nothing but you is reflected in my eye.' The second sentence's さ is a masculine assertive particle — 'for real, I tell you.' Highly romantic.