hey,

i've literally been searching and hunting for a manga i read back in 2008. unfortunately all can remember is

it was a young boy perhaps 16
he wore all black in like a suit or long jacket which he rolled up his sleeves
while he was in a park he was bitten by a vampire and turned
He fights against himself in a mental battle of it being wrong to feed on living things
his main objective was to hunt down the vampire that turned him
it had a graphic style like soul eater

i remember a park, it was in alot of the scenes.

if anything come to mind even if slightly off my description i would love to hear from you
thank you.

Your description reminds me of Darren Shan, though some parts are inconsistent. Going to throw this out there and hope it is the one you're looking for.