Invitation Phallic Azuma Rin(2015)

Rin, a married woman enjoying a peaceful life, finds herself in a predicament when her husband's younger brother comes to see the small house they recently purchased. This encounter leads to an unexpected encounter with a man with a massive penis… The brother's penis, which approaches Rin, is larger than anything she has ever seen or experienced before! Overwhelmed by its size, Rin's lower body becomes addicted, and she soon finds herself unable to be satisfied by anything but a huge penis

Official site