Place it as the closing beat after a confession or compliment appears on screen, and let it be the final line with no follow-up gag after it. In a montage, put a cheering reaction before it so the affectionate reply ends the sequence.
About this sound
This is a short 2.9-second voice clip in Portuguese saying 'Eu tbm ti amu muitu,' a cute, misspelled way of saying I love you very much too. The drawn-out vowels make it feel sweet, playful and a little shy, like a soft reply rather than a grand declaration, perfect for an affectionate reaction.