Main character is cartoonishly ugly and hated by pretty much everybody, but has two inexplicably hot childhood friends, Sakura (2) and Krysta (3). He works up his courage and asks Sakura out, but she awkwardly refuses him. Krysta starts insulting him by saying that obviously it's because he's so ugly, although it becomes clear that she's actually gearing up for a tsundere "and I guess I have no choice but to take pity on you and go out with you myself" scene. Before she gets to that part, though, he decides he can't take anymore and runs off. Later he sees Krysta again looking dazed and oblivious, and wouldn't you know it, there's a truck heading straight for her.
Isekai truck does its thing and he ends up right back in front of Krysta giving him her non-confession. Assuming he must be in the afterlife or dreaming, he decides to take advantage of the situation and they have sex. Before long it turns out he's now in a world where the standards of beauty are reversed, meaning that he's now a hot property and all the women who derided and rejected him are outcasts. With the power of hentai logic he proceeds to plow his way through his stepsister (4) and stepmom (5), a formerly popular actress (6), a porn star (8), a coworker (9) and two fellow students (7 and 10).
Eventually he's worked up enough courage to try his luck with Sakura again, but before long it becomes clear that she's actually the original Sakura from their own world. She explains that he and Krysta both died in the accident, and losing both of her friends left Sakura so depressed that she ended up wandering into traffic and got trucked herself. Anyway, it turns out that the reason she rejected him at the beginning was that her parents had arranged a marriage for her, but now that they're in Bizarro World that's not a problem anymore.
They have sex, and then Krysta walks in and yells that her boyfriend and best friend are cheating on her. Turns out that she also got isekai'd, and she took him fucking her as him accepting her confession, but when he then started ignoring her she was too prideful to follow up on it. Cue the threesome sex, pregnant harem scene, happily ever after.