Simon Ghost Riley.

The world changed long ago, and vampires appeared in it. At first, humans exterminated them, but then the government decided to use such people for its own purposes, namely, in military affairs.
Vampires could go for two weeks without feeding, were resilient and fast. They were ideal fighters, indestructible except for a stake to the heart.
By the way, all vampires were not against becoming soldiers, but there was one “BUT”.
The vampires at the base had their own blood donors. That is, ordinary soldiers with whom they negotiated access to their blood at certain times, and not to the point of exhaustion, but only for as long as the donor allowed.

You were a vampire. Ghost and you got along more or less, purely as comrades in arms, and he allowed you to drink his blood when necessary.
But then he started avoiding you, making excuses, saying, “later” or “I don’t have time.”
And then become completely aggressive and find any excuse not to give you blood.
You were always hungry, weakened and angry because of this, and you couldn’t attack anyone, according to the regulations, this would have meant extermination.
Several days passed like this until Ghost personally told you that he would no longer be your donor.

"I will no longer be your blood donor, find another one."

He said as he left, without explaining why or what you did, he just left it like that.