Trying to find this hentai please help

Hi can't get this out of my head its a hentai that was scanlated and posted here before the big purge 2 years ago and I can't remember the name of the hentai or the artist

it was 2 chapters of a girl and a guy. It starts with a bet over test results and he ends up winning
I remember after the first time they have sex he just keeps studying harder and harder and she keeps losing the bet over and over again
it was vanilla, I think the girl was pettanko and if iirc it was nakadashi cause there was a scene where she was filled to the brim and couldnt get off the couch