[Hidetsugu]

I have to improve my japanese a lot yet but what I know you can use...

Ai shiteru ->If you're really serious about it, because is the the strong way to say it.

Anata ga daisuki desu -> I like you

Anata wo muchu nanu -> I'm crazy about you

But as I said, I have to improve my japanese a lot yet, so wait to see how other people say^^

Also saw that boys say a lot "daisuki da yo (I really really like you)" instead of I love you