From MangaHelpers:
Her name was Megumi Takahashi, and she was his first love. Okamoto's daily routine was to leave his house early so he would be able to see Megumi walk to school, never daring to speak to her. He only had one chance to talk to her, and then she disappeared from his hometown a half-year later.
Four years have passed since she moved away. Okamoto was looking through his daily porn stash when he finds out the porn he's watching starred Megumi under the name Chiemi Mizutani. Furthermore, Megumi ends up working at the same company that Okamoto currently works. Okamoto's love life is going to face some exciting times, for better or for worse.