If you're looking for manga similar to Shin Kounai Shasei, you might like these titles.
Includes the following chapters:
When Ogura starts at his first real job after college graduation, the last person he expects to meet there is the adorable Yumi from his high school days. He used to be her upperclassman, but now not only is she teaching him, she's also grown into quite the voluptuous beauty! Ogura simply can't help falling head over heels... but is a relationship like that really possible between coworkers, even with all the happy memories of the past?
Includes the following chapters:
Summer vaction's the ideal time to create memories, but what if a night of fireworks leads you to the sweet girl of your dreams? And can a stress-out "dog buddy" prove to be the perfect stormy companion? Sometimes you just need a little push to make an ordinary relationship extraordinary!
He likes to watch women's butts from below when climbing the train's stairway. One day, his favorite girl fell and landed on him butt-first, breaking his arm. She then offers to cook for him while he's injured for a month.