https://www.dlsite.com/books/work/=/product_id/BJ01020745.html
As always, please support the artist and buy his works.

NTR approach

"Kazu, there's something I want to tell you..."
Kazu (Kazuma) and Hinano are classmates and childhood friends.
But Hinano is concerned that Kazu has never confessed his feelings for her.
She wonders, "Maybe I'm not attractive..."
One day, when Hinano and her friends were having karaoke with other senpai, Yuki-senpai, who was standing next to Hinano, approached her.
Hinano confided her worries to Yuki.
Then, he told her to change the place and they went outside. There, Yuki told Hinano...

Same author: https://comiko.net/series/72781/is-it-wrong-to-sleep-with-my-best-friend-s-boyfriend
https://comiko.net/series/98615/yokujou-shisugite-okashiku-naru-seiyoku-0-otoko-no-honki
https://comiko.net/series/79446/forceful-insertion-into-such-a-tiny-body-a-mean-boyfriend-s-messy-experiment
https://comiko.net/series/100962/ueta-otouto-ha-watashi-nokarada-wo-sakushu-suru

捏吗,chrome的逆天翻译,我在外面看标题吓我一跳

Base +8, skyscraperxx +5

Thanks for always bringing these offers to our attention. The rest of the series is available for half price ATM.

Not sure about whether the "netorare" or "cheating" tags are applicable here, though. Sure, it's in the title and the series as a whole is very much NTR, but this first chapter in particular doesn't actually have any of that content, so... I don't really know about the correct way to do it in a case like this, on this site.

Base +10, Coledas Ukgent +14, bloody_blade +28, yupokamusi -8

Spoiler:

The girl and friend reunite and seemingly date, but in a kind of disappointing surprise ending, the girl finds that she isn't satisfied by sex with her childhood friend and continues fucking her senpai (and his random friends) behind the childhood friend's back, even though she still claims to love the childhood friend.

I say surprise because it was kind of unexpected since the girl's inner thoughts aren't shown all that much through the series.

Base +16, Coledas Ukgent +14, molenewe +6, vjbeal96 +8