The calm sleepless nights
Impervious to feeling
Ever forgiving

^ I get so captured with such dark, vivid scenes.

The shadows of thought
Lay siege to my emotions
Never relenting

^ This is my favorite part. But I think you should make 'thought'..'thoughts' as it keeps the flow between shadows..thoughts...emotions

Sleep overtakes me
Mercy to a restless mind
Torture to the soul

^ It's quite descriptive here.. I like how you ended with two 'to' .. It gives more depth..

I really seek for Dark.. and Sad poems.. they are just my favorites.. and you made a great job with this form !!

FIVE

Within this poem there is a sense of pain and tiredness..an escape from the overbearing weight of sadness..very nicely done.

Wonderfully penned Senryu. very expressive write.