What's this hentai?

Some more details from myanimelist

Does anyone know the name of a pretty long (like, 5 or so chapters i think) manga about a sex competition, where the guy has infinite stamina except with one girl, so they're partners and end up falling in love? It's one of those things where they treat the idea of a high school sex club like any other sports club, and they do actual exercises to prepare and it's an established institution that no-one in the world thinks is weird.

here's some details that should make it easier to figure out, if you've read the thing I'm thinking of:

-the actual sex competition is a two partner to a team sport, with teams getting scored together based on their performance and how long the guy lasts (the protagonist guy's thing is that he can cum a ridiculous amount of times without needing to stop and for some reason there's a technicality that makes that ok, because of course there is)

-The girl comes from a family of famous sex competitors but is initially not super excited about doing it, and is basically just trying to please her family til she falls in love with the dude

-the word that they use for the sex sport is definitely a japanese word, and starts with "s", I think.

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I feel like a complete idiot for forgetting the title and character names after reading the whole thing 1 and a half times. I thought it was actually a really good sorta surreal romance story, and it was well-drawn and funny, so i'd really like to track it down. if anyone knows what i'm talking about, i'll be super thankful to you!

EDIT:
perhaps one thing I can add to this: I saw english versions of it being posted on galleries in late 2015 to early 2016, and there was also the beginnings of a (presumably fanmade?) colored-in version of the same manga.
Modified by collok, Apr 21, 2016 9:35 AM

Sport is sekijo (spelling unsure ) the comic title translated was -- straight line to love have to get back home b4 give further info.

Gonna piggyback off this to try find one I've been looking for for ages:

>Fairly long doujinshi
>Starts with boy protagonist on train
>Accidentally grinds up on older woman who gets into it and he cums in pants
>She takes him to a bathroom stall at the next station to clean him up and they fuck
>Later, protagonist meets up with a manga store owner or some shit
>Takes him to a private room and makes him read h-manga before they fuck

Ring any bells?

Artist- kisaragi gunma
Title- suki ni nattara icchokusen
Translated title- same as prev post i made
Sport-seikoudo
Translators-triplesevenscans
Chapters 6 plus final is seven for 202 pages
There all the details i have as promised

Sorry none here too similar to many shorts ive read

Similar request:

Magic knife is used to cut people and turn them into costumes that you can wear, any help is deeply appreciated!