Kyuuketsuki ha Shinzo no Yume wo Miru

Shuri is an orphaned college student who was raised by his (very) distant cousin, Hisato; a centuries-old vampire who dreams of one day meeting his soulmate. Hisato will have sex with pretty much anyone in the meantime - including Shuri - but he refuses to commit himself to anyone less than the one destined to be his "heart". Shuri wants to be his "heart" more than anything, doing his best to chase away the string of enamored humans who offer Hisato their blood and body, but can he convince the vampire he loves that the two of them belong together - forever?