Note: Volume 1 is Josei manga. Volume 2 is BL manga.
V.1 - Kare wa Onna to Shita Koto Nai. (Released in Feel Young in 2013, vol. is in 2014.)
V.2 - Kare wa Otoko to Shita Koto Nai. (Released as spin-off of the first vol. in Gougai On Blue in 2014~16, vol. is in 2016.)
Yukio is a normal salaryman who one day becomes relatives through marriage with his former classmate Hijiri, who prefers to dress as a woman. Now brother-in-laws in a sense, Yukio and Hijiri meet again spend time with each other. But, when they kiss during a drunken moment, they realize they might have a deeper relationship than just friends and brother-in-laws.
Official English Translation (Only Volume 2)