Here is a lightly edited subtitle file I originally found on SubtitleCat.com. I believe it was a DL machine translation, so it did need some work.
My standard edits, besides just simple translations/conversions, include fixing some of the tenses, some of the pronouns, capitalizations, search/replacing "I'm going" with "I'm cumming", "So comfortable" with "Feels so good/great" (Kimochi-ii only means comfortable in some uses-rarely the JAV ones, LOL)
My personal edits, which are just my quirks (because I translate them for just me) include:
1) I try to leave titles/honorifics in japanese, but translate the same word if it isn't used directly. So, Mio (the girlfriend) calls her older sister directly as "Oneechan", which is the familiar (family) way of calling her older sister. Yuuki (the boyfriend) calls her "Oneesan", which is the more formal, non-family honorific for an older woman. I left these as is. But, when Iroha (the hot cheating older sister) refers to her sister to Yuuki, as 'my sister', I translated that to sister to english. Its just clearer to me to translate to make clear who they are talking *about*, but when they are talking directly to the person, I leave the japanese title.
2) I didn't do it with this one, but lately I have just started removing the "Kimochi-ii/So comfortable/Feels so good" subtitle text completely-in a lot of cases it is just mumbled/whispered/uttered, not as actual phrases, but more as emotion. I don't think adding the subtitles below it constantly really add much-I assume most people understand they aren't missing some critical dialogue here. But maybe others want it all.
Anyways, here is ADN-337 Summer Vacation In The Hot And Humid Countryside. I Drowned In Sweaty Sex With My Girlfriend's Defenseless Sister, with Iroha Natsume