https://www.pixiv.net/user/6948350/series/86431

There's an essay for each of the "Parts" of this work.
With google translate, the plot basically goes:

MC lives with his single Mother, his Dad died, MC loves his Mother and keep her feeling as much as normal as possible. His mom ends up dating his friend and we see things from MC perspective.

Mom and MC-Friend do couples things which MC only having gut feelings of what they are doing but later on it became obvious how much of real couple they are. MC became a good 'ol cucked in this kind of stories, he doesn't like that shit but what can you do, they just couple doing couple things and both MC-Friend and Mother doesn't being a villain towards him. This shit slowly tormenting him.

At Page50, it seems like MC-Friend is serious with his relationship with Mother, he finally propose to her with ring and of course Mother hella happy with that so they fucked like rabbits afterward. Mother ends up pregnant after 17 years. MC-Friend parent support their son's decisions and it seems like he buy the ring with his own money too.

At Page52, After MC-Friend became an adult (18yo) they decided to married for real and they did. Of course they live together from now on and of course MC gonna get the cucked dilemma of hearing them fuckings every night and all that jazz. The good 'ol live of MC living alone with her caring Mother are gone. She's not "The Mother of MC" anymore, she's "The Wive of MC-Friend" now.

At Page61, Mother being a single mom has face so much hardship, as a son, MC really wish happiness for his mom, that moment finally came now but it's not the kind of happiness that the MC expect. There's so much dilemma MC faced here but seeing the child of his Mother and MC-Friend and her new happiness really broke him into pieces. MC see that her mom can be happy without him and with this tormenting feeling he had, he decided to live alone (he use going to college as an excuse). Mother of course felt sad and lonely when she hears that but she support his decisions. MC think that he can burried his hidden feelings for his mom to the graveyard.

At Page66, lots of inner-feeling stuff here before the climax. MC and Mother spend the night alone reminiscing their good 'ol time together before the depature (idk where MC-Friend is, maybe late at work). Those moment make MC cry and Mother said "MC if you're lonely, you don't have to force yourself to go. If you're gone, I'll be lonely too." hearing that made MC snap, he can't hold his feelings any longer and he push her down. Sad Sex (Rape) coming through.

Mother resist at first but when they finally meet eye for an eye, she understood everything and let her son do what he gotta do. MC blur out his true feelings and everything else to her. After it ends, Mother say the classic "I'm sorry I didn't notice" with tears. MC apologize, he just destroyed everything.

Later they parted without saying any words, they both holding their tears. The moment MC walk away from the house he can hear her Mother cries but he didn't turn his back on. Finally at the bus after he's far away, the feeling of loneliness and loss got to him and he cried over the picture of MC and his Mother.

"While thinking of happiness with my former mother, I will never return." - The End.
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Extra:

Six months have passed since then, and I have been busy every day as a college student. She was able to work part-time in class, and for the first time she was able to. That day, it was the encounter that comforted me who shed tears in the bus. (As expected, I could not honestly tell why I was crying). I can say that my college life is fulfilling.

At that time, MC received an email from MC-Friend:
"Mother was pregnant. She is 6 months pregnant now. Would you please come home for once?"

The character design of the mother -- or at least her hairstyle -- makes her look like a grown-up version of Takagi-san from Karakai jouzu no Takagi-san.

Base +34, okmonger +5, Xuy -5, suratkabar +11, your_name +6, Sylphvine +6, Coledas Ukgent +12

這劇情讓我硬不起來，話說苦主讓我想起甘城輝煌樂園那個姐控老鼠

Base +6, Xuy -5, suratkabar +11, Coledas Ukgent +12

I love the character design and despite it not being translated the summary is still somewhat beautiful.

Base +12, rising11 +9, JoseML +6, Xuy -5, suratkabar +11, lionsroar89 +7, Sylphvine +6, Coledas Ukgent +12

So the second baby coming is the son's? lol.

Base +6, rising11 +9, Ryougi +11, okmonger +5, Justray +7, suratkabar +11, Xuy -5, your_name +6, assiap2 +6, Sylphvine +6, Coledas Ukgent +12

the art is really good

sadly she only gets one pregnant sex image (so a 1 page pregnant sex scene)

Base +8, Xuy -5, suratkabar +11, Coledas Ukgent +12

I like the media used to create the artwork. And I especially appreciate your effort, OP, to preserve the original context included with the work. Amended from four stars to five in consideration of this above and beyond effort.

Base +8, Xuy -5, suratkabar +11, lionsroar89 +7, sonnytag123 +14, Coledas Ukgent +12

Not my kind of story, but your effort in machine-translating it is awesome, I really appreciate it.

Base +6, Xuy -5, suratkabar +11, Coledas Ukgent +12

hope this get translation

Base +6, Hyper_De +7, Xuy -5, suratkabar +11, Coledas Ukgent +12

looks like this is actually drawn on paper and scanned. Seems like hard work!

Base +6, Xuy -5, suratkabar +11, Coledas Ukgent +12

I love wincest but this is just sad. Rare occasion where I'm thinking he should have kept his feelings to himself instead of breaking his moms heart and scarring her for life....

Base +6, Xuy -5, suratkabar +11, sonnytag123 -11, ScrawnyJohny -6, lionsroar89 +7, Coledas Ukgent +12

Umh, the betrayal is there, even if the mom doesn't recognize it...

A woman has the right to restart her life,
The problem here was that she disregard her son place, and disregard her home,
If she got in a relationship you can't use your home as motel if you has underage here.

If you found something similar...

The son should've used legal methods to protect his dad legacy.
Talk with his grandparents or family in his dad side.
Put their photo and history in cloud social media.
Give a good beating to his ex friend for fucking his mom.
Search for mental care.
Buy a 9mm gun.

Base +6, darkmasterpui -12, sonnytag123 +11, falae +6, RaizelX -7, assiap2 +6, cbdyourmom -8, nantyp +6, Coledas Ukgent -12, suratkabar -23, DonkeyFace -7

要结婚做爱能不能给老子滚出去，在亲爹房子里干这事恶心谁呢？

Base +6, chen19958 -6, cbdyourmom -8, meter8 -4, lovebigbreastmilf +2, Coledas Ukgent -12, lwy121011 +3, mnbvcxzohhi +6, suratkabar -24

差点看成高木同学

Base +5, Coledas Ukgent +12, suratkabar +24

이건 친구놈이 개새끼인거임 그리고 친구부모님은 이해를 못하겠고 엄마는 씨발년임

친구 놈이 씨발놈인 이유는 지 친구를 생각한다면 저따위 짓을 하면 안된거였음 엄마도 마찬가지임 아들을 조금 이라도 생각했으면 저러면 안됬던 거임ㅠㅠ

Base +3, Coledas Ukgent +12, suratkabar +24

Kill the leech, torture and kill the whore, take the brat and put it into adoption

Base +6, DonkeyFace -7, lkoofu +10, suratkabar -24