Ai no Chikara

The main character, Kouji, is a medical device salesman who tries to live a fulfilling life, but is overwhelmed by an everyday routine. One day he meets an innocent nurse, Karen, at the hospital he is attached to. Being charmed by her cheerfulness and gentleness, he still can't make one step further, and the distance between them is just increasing.
Holding his feelings towards Karen, one day he goes to a local bookstore and finds an amatuer adult photo magazine. Glancing through it he feels that his hidden desires are awakened...

[Translated from Getchu]