I've tried translating this. It's mostly OK, but I'm not sure what オカズに means in this context. What's for sure is that the little sister masturbated in his brother's room, he sure looks pissed off.
May be it's too late to respond now three monthes've passed by. But let me tell you "okazu " means an object about which one think when masturbating. So the little girl in this picture masturbated in her bro's room thinkin' about his friend.
