This is not an NTR / Cuckoldry themed work.

Kengo, a guy nearing thirty, is an ordinary old company employee.
He has been dating a woman named Yuuna for two years. She is a strong-willed and selfish woman, but to Kengo, she is the most attractive woman he has ever met.

However, just as he was thinking of eventually marrying her...
A slip of the tongue by Yuuna leads to the discovery of her having an affair!

However, instead of apologizing, Yuuna bursts out in indignity instead. Kengo is dumped and abandoned. Depressed and devastated, Kengo wanders around town aimlessly...

What a miserable experience... having one's girlfriend cucked by a handsome guy. There is no greater misfortune.
Nothing could fill the hole in Kengo's heart that was left gaping open by losing the best girl in his life....

That's when a crazy thought comes to Kengo's mind....
How about I hit on and pick up the cute store clerk at the bakery! A reckless and unfeasible plan.

In desperation, Kengo riles himself up... "I don't give a damn what happens!"
Prepared to possibly even be banned from the bakery... he rushes inside and...!?

(Source: DLsite)

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[Note: This has 2 near-identical versions, one is the original doujinshi, the hardcore version which is a single book that has black bar censorship; the other is a heavily censored softcore version published by FILL-IN, split into 2 chapters; The covers are slightly different but the story is the same.]

Published as "Kanojo o Netorareta Kedo Boku wa Shiawase ni Narimasu Tennen JK to Nukumori Ecchi" by FILL-IN.