Buy the original product to support the artist(i.e. Mochimochi Dou) and thank you Crestina for uploading these five artist Cg sets presented by Mochimochi Dou
Summarized from the dlsite link: Protagonist's father suddenly brought home a wife who will live with them. The protagonist falls in love at first sight, but he knows it's wrong, so while he tries to sort out his feelings, he is very awkward around her. But she persistently tries to connect with him. Almost as if he is her real son, she endlessly pampers him. Against this defenseless pampering woman, he starts to approach his limit.
This author usually has a twist at the end of his/her works, so here are the last 3 pages (103-105): The last 3 pages (103-105) are about the mother's inner monologue where she talks about how she had a child previously. Not sure how they separated because my Japanese sucks. She goes on to talk about how she hired a private detective to find her lost son, and then found out that he was being raised by a man. She became that man's wife to reconnect with her son. She felt bad because the man was an honest husband, but for her son she was willing to do anything. Then her last sentence is "Ah, I love you. More than anything in this world, only you I love, my beloved son.
This is the raw text from the last 3 pages in case anyone with a better understanding of Japanese would like to take a shot at it. It was taken with google's OCR, so there might be some incorrect/missing characters. I did not use google translate, just their OCR and then JParser/Edict2 to understand the meanings of the words and phrases.