Tsukiattenai noni Fuufu Yattemasu.  

Were a Couple Despite Not Dating, 付き合ってないのに夫婦やってます。, We're a Couple Despite Not Dating, Una pareja sin citas

Kiichi Amakasu is a gay man who lives with his straight best friend, Ryuunosuke Shibata, while raising the latter's niece, Mako. Despite facing challenges in balancing child-rearing and work, Kiichi has developed a close family bond with Ryuu and Mako. However, there is one thing that Kiichi has kept hidden from everyone - his longstanding unrequited love for Ryuu. Although he had planned to keep these feelings concealed forever, a drunken night led him to sleep with Ryuu, causing emotional turmoil in the story of this painful unrequited love and family ties.