Hitozuma Mahjong 2

Synopsis

6 years ago - the young student protagonist (while living with his parents?) had an unrequited love for a young OL - Sakurazawa Nanako - who lived alone in the next apartment. Sometimes he'd hear sounds of Nanako in her room separated from his by just the wall, especially the sounds of her showering. He indulged in masturbation every night while imagining her shower scene. He found that he could peep into her bathroom if he leaned out from his balcony. However, she also had had simple conversations with him, knew that the he had begun job hunting, and even given him a job guide book that she had used. To this end, he entered her apartment for the first time with a throbbing heart.

One day he crashed into her while she was taking out her trash. Things became awkward when used condoms spilled out, and he began to intensely masturbate every night imagining her sex life. Nanako eventually noticed the feelings of the young student, and promised him "I'll have sex with you once you've passed the employment test"! The student kicked it into gear and gave his all to studying, but then shortly afterwards, he found that Nanako had suddenly moved away. He became desperate, spent his savings on losing his virginity in the late-night city, and abandoned the employment test. Eventually he slipped unnoticed into the underworld of professional mahjong masters.

Still to this day, he seeks opponents for the game, aiming for money and older married women.

(Adapted from the description on the Japanese DLSite.)