Wakaba or Ayame.
What if, instead of ending up with Mikoto or Haruna, the protagonist were to form a deep connection with either Wakaba or Ayame?
This is a sweet, steamy after-love story filled with romance and passion!

--Wakaba Chapter: "A Future Painted in Fresh Green"
Just before summer break, Wakaba confesses her feelings to Yuichi. After some twists and turns, Yuichi finally asks her out directly, and the two officially start dating.
While continuing her club activities, Wakaba enjoys her sweet days with Yuichi. But as summer break nears its end, she realizes she hasn’t done any of her homework. Panicking, she dives into her assignments, with Yuichi stepping in as her strict coach.
The two study hard at Wakaba’s house, but she quickly gets bored and starts teasing Yuichi with a little cleavage… Unable to resist her bold advances, Yuichi gives in.
Between tutoring and their steamy escapades, the days fly by.
When the new semester begins, Wakaba barely passes her exams thanks to Yuichi’s help. Soon after, the autumn track and field meet arrives.
Amidst the cheers of her classmates, Wakaba sets a new record and wins the competition, becoming a school celebrity overnight. Her popularity skyrockets, drawing attention from both boys and girls.
Though Yuichi and Wakaba’s relationship is public, some students start whispering that they’re mismatched—that Wakaba is too good for him.
Wakaba, who works hard and achieves her goals, shines brightly. In contrast, Yuichi feels like he has nothing to offer. Maybe they really are mismatched…
Yuichi starts to feel a subtle distance growing between them. Sensing his unease, Wakaba grows anxious and confused.
What will become of their love as this emotional wall rises between them?

--Ayame Chapter: "Engagement to Newlyweds (A Couple Trying for a Baby)"
After fully accepting Ayame’s infertility, Yuichi begins dating her. From mid-summer to the end of the break, he visits her apartment almost daily, making love to her and pouring his affection into her.
Even after summer ends, Yuichi continues visiting Ayame, spending every night with her. He desperately wants to see her pregnant, to give her peace of mind. But despite his efforts, Ayame doesn’t conceive.
Though Yuichi feels a growing sense of urgency, he never gives up, encouraging Ayame and continuing their attempts to have a child.
Time passes, and after graduating and starting his career, Yuichi proposes to Ayame. The two officially become husband and wife.
Months later, Yuichi’s unwavering love and determination finally pay off—Ayame becomes pregnant with his child. Overjoyed and relieved, the couple celebrates this miracle.
Despite her growing belly, Ayame continues to make love to Yuichi, wanting to show her love for him.
As the days go by, their baby grows steadily, and the time for delivery arrives. Though Yuichi is worried, Ayame pushes through and gives birth to their long-awaited first child.
While raising their newborn with love, Yuichi and Ayame set their sights on a second child, passionately continuing their efforts to expand their family…

[Translated from dlsite]