Oh I'm building a new mrm wedding inside my head thanks to it!
Let's see... Their wedding is in a garden full of flowers, they both love plants and the outdoors, they chose to wear each others colours instead of their own, they tried to be more traditional keeping apart on their last night, mob didn't want to but reigen convinced him it would be fun, mob can't wait to be married while reigen is nervous he'll mess something up and is also very insecure. In reigen's opinion it was silly to have either of them waiting at the altar so they decided to meet and walk together, mob can't help but rush to reigen and dip him over for a kiss before they even get to the altar, it leaves reigen very flustered as their vows are said, mob isn't good with words so his vows are very simple, Reigen can only say it to him so he hands him a piece of paper (folded too many times and almost ripped from nervousness) it's a bit confusing for the guests but everyone could see the love in their eyes. Ritsu and Teru are mob's best men, ekubo and seri are reigen's. Mob was all too eager to tell ritsu, ritsu wasn't happy about it, he'll never like reigen and get over his romantic love for his brother, teruki had a crush on mob and on reigen but is happy for them. Teru finds ritsu bitter and angry and on the verge of ruining everything and offers to fuck to let out some steam, it works a bit too well, but they have mixed feelings about it (they are both in relationships that go nowhere with shimazaki/shou)
Ekubo has a deal with the sg he got the body for the day, he's very very happy but acting aloof about it, sg's body is weak to alcohol ekubo drinks and ends up babbling how much he loves mob+rei.
Serizawa witnessed mob dragging reigen to the toilets for a quick one (he was in the other stall, he heard it all) and that is why he's so uncomfortable looking.
Mob and reigen practised for their first dance a lot, reigen insisted but the moment the music hit it felt like it was just them, the weight of their rings so present in their minds, they simply swayed to the music forheads pressed together.