JUST 20CM AWAY FROM YOU

Just 20cm Away From You summary:

Chapter 1-3, 6: Hidaka Atsushi and Sakaki Youichi have known each other since senior high school, and are now going to the same college together. They share a "rotten relationship", according to Atsushi, who, at one time, gave in to temptation and slept with his friend. Disgruntled about having to play the "bottom" role (since Youichi is 20cm taller than him), Atushi seeks out a smaller, cute boy to whom he can play seme to. Chapter 4: The Melting Point Chapter 5: Smiling At Tomorrow's Sky