Red Beryl ni Sayonara by Michinoku Atami

Summary

Plot: Since childhood, Akihito has been convinced of his own worthlessness. One day, as he’s on the verge of giving up on life altogether, a stranger steps in to save him: Kazushige, a vampire who has been living alone for a long time. Akihito is touched by Kazushige’s actions and begins to visit him frequently, but after that initial moment of kindness the other man always treats him coldly, attempting to drive him away at any possible moment. But Akihito will not be deterred, for he has finally found something that may lend meaning to his existence.