Story 1 (ch.1-2 + 6.5): tattooed Yakuza (seme) x dry cleaner (uke)
Story 2 (ch.3-4): university students ?, already lovers, seme thinks that uke is innocent
Story 3 (ch.5-6): age gap, childhood friends, uke (probably) comes back home after 6 years and meets his best friend's younger brother
Koiiro Rain