Our lead MC was raped and manipulated back during highschool. The perpretator grew and fell in love with his childhood friend who's turned out to be an actual lolicon. She tried to win back his affection by various methods, eventually in highschool, she knew this lolicon and our MC are both friend, trying to spark jealousy by getting close to MC, which to her surprise, instead of this lolicon getting jealous, he 100% all for it and support both of them.
After "the deed" has happened, our MC, confused as hell, and have no experience with women, were keeping his distance to this woman, well, to make it easier, let's just call this woman as Nozomi and our MC kouta, and the lolicon Nicchi. So Kouta distanced himself from Nozomi for some time, until graduation, Nozomi is also never tried to reach out to him, later eventually became pregnant with a daughter named Kanau, went and raise her for 9 years all alone, believing herself to be guilty of using Kouta for her scheme of which did not worked either. During those 9 years, she also met another man, a doctor, whom resemble Nicchi, and got another child with him 🤦♀️. This child has a rare health problem, forcing her to go into a huge debt with the Yakuza. She went to do various odd & dangerous jobs in order to paid all of her debt in full and have the money to raise both kids all alone. (No need to worry though, it's not "that kind of job", she's surprisingly capable and even could pass as a deadly assassin (lol) since her upbringing raised both her and Nicchi with some twisted teachings).
Eventually after one year, she decided to take back Kanau, who at the time, already developed bond between her and her dad, as well as all the residence, as well as the kid from the doctor, who is now well-off, and trying to live somewhere secluded. At this point, it's a race between Kouta and the doctor as for who find and could convince her first, of which our MC lost the race miserably due to some factors, first, she picked the doctor due to his resemblance to Nicchi, while with Kouta, it happened far earlier and she were just using Kouta for her convenience. And second, the doctor is already well-off while Kouta is just some manga author's assistant and is also a weeb (though the doc is also a weeb but it kept secret from Nozomi).
Kouta feel into depression for a week, one fellow co-worker, Haruka, who is also a residence of the same apartement tried to cheer him up, she had feeling for him at the time (was a good plot building too but wasted), but what it does, is just convinced Kouta to try and get Kanau's back from the grasp of Nozomi & Doc.
After that, there's this time skip, basically alls end well, the doc bring his kid and visit Kanau & Kouta from time to time in order to maintain brother-sister relationship between them. Kanau lives with Kouta as father and daughter, Haruka DIDN'T ended up together with Kouta but is implied that they hooked up one time and she's now a single mother and also a famous manga artist working for a company while trying to raise Souta, his and Kouta son as a single mother.
The reason of why Kouta didn't ended up with Haruka mainly to trust issue he got from Nozomi, and also from another girl, the apartement landlady, whom he was infatuated with. She was an 19yo third-year highschool student who is secretly married to an old manga author who is also the boss of Kouta & Haruka at the time and it shocked everyone when things are revealed. Because just not too long before that, Kouta seems to think that he finally able to moved on from Nozomi to Taeko, the landlady of the apartement but was slapped with the hard truth of her being his boss wife. The boss is not manipulative per see and he really is a really nice guy too, but the nature of his relationship with Taeko was also due to some fucked up circumstances.
Taeko was the rightfull successor to the apartement building, from her mother's lineage, who were born and raised into a rich elite family, but rebels and became a working girl instead (it is another fucked up story on it's own but anyway, this basically another reason as to why Kouta is having trust issue)