I had to write a love letter in English so I did one from Creed to Train. Creed is in prison for unknown reasons and I will write a second chap with Train's reply if requested. May be slightly clichéd
Warning: yaoi

Disclaimer: I own nothing you recognize

To my Hearnet,

My life has been a desert drear since the moment I was carried off to prison. When I get out of this place I will track you down, so that we can be together. Once I get out, we will destroy the Chronos, like our destinies' say, and they can be finally fulfilled. I look at the dank wall and wish your golden catlike eyes were here to light it up, make my life wonderful again. Your happy-go-lucky would really cheer up my world. I watch the rain fall outside and am reminded of all the missions we completed together while still part of the Numbers. Hades shining in your hand while the rain fell around us. I dream of you at night, your dark brown hair blowing in the wind, in most dreams you are wearing your black trench coat but lately you have been wearing your outfit with the strange circles on the blue coat. I have even etched your number onto my wall, XIII.

I miss you dearly, Train. I will always miss you and you will always be in my heart, I will bring you to my side and heart, all I have to do is wait patiently. One day you will crumble to my will and gice me back my Kotetsu.

Yours only,

Creed