Ushiro no Seki no Gal ni Sukarete Shimatta. Mou Ore wa Dame Kamoshirenai.

A high-school boy Sandai, who liked to spend his time alone, accidentally helped the most beautiful girl in his class, Shino, when she fell into a ditch near his home. He let her use shower at his home, and lend her some clothes, although he had never talked with her before. From that day, she started to act like his friend. In fact, she seems to like him...but that can't be! She's the most popular babe in his high school! But what he didn't know was, Shino had never went out with a guy. She was not very good with guys, and Sandai was the first guy she could talk naturally with. As they spend time together, Sandai can't help himself to have special feelings for Shino. A story of a boy whose life was completely changed by a cute babe! (Source: Kadokawa)