It is 愛,The 愛 a bit like one of Chinese in japanese,It is 爱,

If you want to say "I love you" the direct translation would be aishiteru, but a more common way of saying I love you is Daisuke, more directly translated as I like you a lot.

Ai あい 愛

It is "ai", written like this in kanji "愛".

Ai = Love