Danman, thank you for putting this in the proper order!
Quick synopsis:
Takuya is a baseball ace and Minami is his childhood friend and manager of their high school's baseball club. Takuya has been chasing his baseball dreams all his life, and Minami has been supporting him for just as long. Both of them have a crush on each other. One night, he takes her to a baseball field to talk. Minami thinks Takuya is going to confess to her, but he promises Minami that he'll get to Koshien. Takuya thinks Minami wants him to go to Koushien just as much as he does and promises himself to confess his love to Minami after the team makes it. Minami, however, is depressed because she doesn't know how to feel, even though she understands Takuya is going to have to practice hard to get to his dream.
The next school day, she's called out by a third-year student named Ren, who is recruiting for his "event circle", basically a group of party and event planners. He invites Minami to one of their parties to see what they do, and she agrees in order to change her mood. At the party, Minami is impressed by the event as well as by Ren's future ambitions. She agrees to join the circle and gets new friends. Even though they all have that stereotypical "gyaru" look, everyone's very kind - including Ren. Ren eventually seduces Minami and she begins to change her style to match her new friends and devotes more of her time to the club and to her boyfriend Ren. For the first time, Minami feels like she's doing things for herself and making her own goals. Takuya doesn't know any of this is happening.
By the end, Ren and Minami are completely in love, working on achieving their goals. Takuya and his team make it to Koushien, with Takuya getting enough attention to give an interview on TV. He plans to confess his love to Minami the day after he texted her on the last page, but he doesn't realize it's far too late.
Extremely light one-sided NTR, but more realistic than your average NTR.
You either chase your dream or the girl, you can't have it both ways in life usually. This is more of a "such is life" scenario, and certainly a much more believable than most netorare. Seems both characters got what they needed in the end: his baseball career and for her a loving partner (unless there's something implying that her boyfriend is forcing her to this).
In other words, had Takuya admitted his feelings on top of his dream, things would have turned out fine for him. The guy deserves to get cucked for thinking the rest of the world will wait for him.