Kono Tabi Osananajimi to Karikon Shimasu

Taichi, who has been freeloading off his girlfriend, gets dumped and has no choice but to go back to his parents' house. The person who knocks on his door is his childhood friend, Ryousuke, who grew up to be a handsome man.
After they met again for the first time in years, Ryousuke suddenly proposes to Taichi. Confessing that he has always loved Taichi since they were kids, he requests that they apply for Provisional Marriage ー a system where couples can try being married for a maximum of six months.
Despite being overwhelmed by Ryousuke's intense feelings, the words "you don't have to do anything, so just be with me" lure him in. Taichi agrees to the provisional marriage like he's just agreeing to be roommates, but then...?

(Source: Houbunsha, translated)

Note: Includes 1 extra chapter.