In French, it's 'Je t'aime'. In German, it's 'Ich liebe dich'. In Spanish, it's 'Te amo'. In Irish, it's 'Is breá liom tú'. In Swedish, it's 'Jag äiskar dig'. But I think they best way to say it, is to be by their side whenever they need someone. Natsu and Valerie have been best friends since Valerie joined Fairy Tail - which was only a few months after Natsu - and had immediately got along. Both raised by dragons. Both dragon slayers. One is in love with the other, while the other is in love with another.