Nao Takanashi loves her older brother Shuusuke to the point where it’s become a real problem. Wishing her brother would see her as a woman, Nao makes not so subtle advances toward him on a daily basis. One day, while throwing out her brother’s extensive porn collection, Nao finds a family album containing photos from his childhood- none of which include any pictures of her! Discovering the truth about her blood ties, Nao ramps up her romantic moves on Shuusuke. Soon, her dreams of monopolizing her brother’s romantic attention are put into serious jeopardy!

[Source: Media Blasters]

Nao looks over her 'Big Brother's Perverted Habits Diary,' looking over Shusuke's misfortune with seeking out various porn.

[Source: Wikipedia]