I just gave it a try and got nowhere, I think the problem is not one of sharpness but one of pixelation.
I do not think anybody will be able to fix this for you but I hope someone will prove me wrong and find a way for you.
P.S. if youre after manga - anime pics then a lot of porn sites have sections devoted to it, granted they are all about fucking but once you crop the pic it's not obvious.
never mind a 3 second search on google.com and I got this.
it's not the same size as yours but that's cause the width is 150 not the height if you want I can crop the side down and make the height 150
there's one called Amime central or something like that... it's pritty good too... Gives you a tour guide that follows your mouse around and explains everything...