I just listened to red and black again and I just had a funny idea:
What if in a somewhat-more-happily-AU-verse, Marius burst into the Musain, and Grantaire begins to tease him just because he wants to annoy Enjolras, and of course Enjolras takes the bait and begins a speech about the fact that romantic entanglements have no place here (never mind the fact that joly, bossuet and musichetta are always flirting with each other somehow) and then, Marius’s cheeks reddened and he begins to talk about that “moment of breathless delight”, etc.
And Grantaire mostly backs him up to (again) annoy Enjolras, but then later he thinks about everything Marius has said about what it felt to fall in love, and it makes him think of how it felt when he met Enjolras - it’s funny because it almost feel similar - and he glances at Enjolras again, who’s now talking calmly with C2, even smiling, and Grantaire’s heart skips a beat and he thinks : “…oh”
(he bursts into Joly and Bossuet’s flat, panicked, in the morning and screams: “I THINK I’M IN LOVE WITH ENJOLRAS IT’S AWFUL” and Joly and Bossuet just stare at him and giggle for ages and then Bossuet falsely gasped: “OH MY GOD I THINK THE SKY IS BLUE” and Grantaire looks so betrayed that Joly takes pity on him and pats him on the shoulder saying: “R, you’ve been in love with Enjolras since the minute he actually opened his mouth in front of you for the first time” and then they pull a Friends thing like “what why didn’t you tell me”/”we thought you knew!”)
(Grantaire can’t deal with the situation, he starts to blush when Enjolras speaks to him, and Enjolras just don’t understand what’s happening but “woh, Grantaire’s cute when he’s trying to be sweet and his cheeks are all pink, isn’t he Courfeyrac?”)
