Yoshioka Akira lives alone due to his father's job and goes to a school in Tokyo. Outside, he seems like a normal high school boy you can find anywhere. However, one thing sets him different from the others: he is interested only in older women.
In his school, there were 3 women that stood out the most:
First is Ayase Shizuku, Akira's homeroom and English teacher. The second person is the school nurse Kuriyama Mishio, and lastly, the cafeteria lady Matsuzaka Chinami. However, he can only admire these three from far away, and believes there's no way to get closer to them.
Luckily for Akira though, he finds many kinds of opportunities to actually get to know these women through different kind of twists and turns, thus leading him ultimately to cross the barrier between the student-teacher relationship, and climb up the stairwell to the adulthood at the same time...

[Edited from Getchu's description]