Erohon to Boku to NEET Oneechan

Older female childhood friend (who is also a NEET) visits her younger buddy to play some video games together only to discover a newly acquired porn magazine "Big Tits Special" that he unsuccessfully tried to hide. Our girl decides her bosom is no worse from those in the magazine and puts forward a bet with some totally rigged terms: no matter the winner, they'll have to have sex either way.