I have set this near the beginning of Dirge Of Cerberus, just before Vincent goes to Nibleheim, after the MRO base has been attacked. He is sat in Lucrecia's cave :)

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My Last Words To You

I'm so sorry.

Lucrecia…
Sitting here, once again, in your cave, I wonder: How long has it been since I have felt your warm touch on my skin? Or how you used to run your fingers through my short, tousled hair? How long did it take for me to adjust to the fact that I will never hear your delicate voice again? The same voice which filled me with a feeling that I haven't felt since you chose to trap yourself in that crystal…
I took so long for the pain to leave me, so why am I forced to look into my past and feel the hurt once again?

I'm so sorry.

I shook my head.
No, I'm the one who should apologise. That day… I did nothing. I just stood there unable to understand your decision to carry out the experiment, on your own child. Your eyes were so fierce, that, if I am honest, you scared me. You think that you have made so many mistakes, but I forgive you.

I rest one hand over my knee and glance at my reflection in the water below your feet.
Deepground. I don't know what they want with me. Only that they think that the beast inside me is what they think will cause the end of the planet. You called it Omega… Innocent lives are being taken.
Why didn't you tell me that you were researching the Chaos gene inside me? Help me find the answer, Lucrecia.

I have to fight. These deepground warriors must be stopped. I will not allow the planet to die. It will mean that our efforts three years ago were in vain.
Yuffie, Reeve, Shalua, Cloud… I am not the only one to suffer from this war. So I will do whatever it takes, alongside my friends.

Standing, I look at your peaceful face once more before turning, leaving the mako crystals to shimmer around the cave, highlighting the beauty of your slumbered state.

"How I wish that it was you beside me…"

I'm so sorry.

Soul wrought of terra corrupt,
Quelling impurity, purging the stream,
To beckon forth an ultimate fate.
Behold mighty chaos, Omega's squire to the lofty heavens.

"When will it all end?"
Will these my last words to you?