Geez, people just through around the word "incest" so much! Look up the definition. The low-life mother just gave her child to a complete stranger due to being a an irresponsible bitch. I find that MUCH worse than a child falling in love at first sight to this guy she picked. So this random kid has to raise a 4 year old child and agrees because he's always been in love with her mom. 15 years later they discover their mature love for each other. She's 19 and he's blah blah blah... you do the math. Seems typical. Cause men are men and they don't think with the head on their shoulders when it comes to hot fully developed women. PLUS...THIS IS JUST A MANGA MADE TO GET "YOUR" ATTENTION. It's make believe! So, if you keep that in mind and just read the story it's a sweet love story.
Papa to Watashi, Kowareta Kyoukaisen - Kemono no you ni Tsunagaru Karada