Marinette, Adrien, Alya and Nino.
The whole core ML cast, I see! HRM
Marinette: A Gryffindor through and through! From what I can tell, even before becoming Ladybug she had a lionheart (even if she was hesitant to act on it). She’s brave and has the strongest sense of justice.
Adrien: Hatstall between Gryffindor and Hufflepuff, maybe? Adrien has a stronger sense of kindness than justice, and he’s incredibly brave, but he seems to be motivated by supporting the people he’s close to over heroics for their own sake? We know from his side story that he wants to support his father in the absence of his mother and from his actions as Chat Noir that he’s completely dedicated to her (and by extension, Paris). It’s hard to know for sure which he’d end up in, and I think it would come down to him wanting to be where Ladybug is, haha.
Alya: *deep breath* I … really want to put her in Slytherin … because she’s super ambitious and brave as hell about putting herself out there, but also really loyal and protective of her friends. She wants to unmask Ladybug and will stop at nothing to get a scoop. OTOH, she’s not just supportive of Marinette but also protective of her feelings. I’m sad that we don’t see more of Alya’s wants and dreams in the series, but for now, I think that she combines Hufflepuff and Gryffindor traits to make a great Slytherin.
Nino: It’s hard to say with this guy just because we don’t know that much about him! (One of the faults of Miraculous Ladybug is that we don’t get much of Alya and Nino’s lives apart from Marinette and Adrien.) He probably belongs in Hufflepuff, since his most character-defining moment was when he was so determined to get his friend a good birthday he confronted Adrien’s father directly. He’s not particularly brave but he’s honest and straightforward, almost to a fault, which feels a bit more Gryffindor, but between that and his kindness I’m going Hufflepuff this time, I think.