Mata Ashita, by Every Little Thing. I love that song... Or Sakura by Naotaro Moriyama... Or Watarasebashi covered by Aya Matsuura (it's a very beautiful ballad, not a pop song)... Or Final Distance, by Hikaru Utada? All those songs seem very good to me, very sort of "i'll miss you and i'll always think of you". They are all good, but Sakura really stuck out in my mind. My friend was in Japan when that song released, when she just got there, I believe, so that song will always be her song in Japan. It's so beautiful and lovely.... here are some translations!
http://www.centigrade-j.com/translat...manaotarou.htm
i hope you find a song!