muse ✨'s manga / #duplicate(6)

I've read this as part of another story on this site. This is the first part, where two men - Amano and Takano - who haven't seen each other in 20 years go out for drinks. They're interrupted by Takano's ex-lover, who mistakes Amano for Takano's current lover and punches him. When he wakes up, Amano is back in high school, in Takano's bed, and believes he's in a dream. He and Takano form a close relationship before he's taken back to the future, to find himself in the current Takano's bed. And Takano is angry, because twenty years earlier, after they'd slept together, Amano seemingly forgot everything about it. Also appears in http://www.mangago.me/read-manga/dorobou_to_hatsukoi/