借り妻－今夜、兄嫁と寝ます－

The protagonist is a fat and not-so-good-looking man called Mitsugu Yazaki.
He has an inferiority complex because of his brother's all-around greatness in professionality and looks.
Because of that, he struggles with socializing, and becomes a shut-in. His specialty is beating games. His lover is his 2D girls through his right hand. He is ultimately living his life as a NEET.
His investment program created with games, however proves successful.
As a result, he manages to leave home and live at a apartment, enjoying his life as a shut-in.
One day, his sister-in-law, Sayuri contacts him regarding his brother needing money to remodel his house.
In reality, his brother needing to remodel his house was just a front. His brother has actually amassed quite a lot of debt from his assets that have gone downhill.