Ryomary

Canon
Ryota is initially shown being tormented by Mary during a gamble, and then using him as her own personal footrest.

After Yumeko defeats Mary in the Rock Paper Scissors game, she goes to the Debt Settlement Gamble, then defeating Jun Kiwatari. A while later, she bumps into Ryota in the hallway. She asks him where Yumeko is.

When Kaede Manyuda and Yumeko started to gamble against each other, Mary sat next to Ryota.

During the Tarot game, Mary worried about Yumeko and hoped Ryota would make the right choice. When he picked a random card, she nearly fainted. She was relieved after the game and was happy with her new friends. But she still scolded Ryota about how close it was.

Kakegurui XX
Mary helped Ryota in the Nym Type Zero game. In the first round, she tells Ryota to show them his cards, because Mary noticed the shuffling pattern Runa used and by knowing two sets of cards, she can also deduce the cards of Miri and Miyo. Ryota trusts her and "drops" his cards. Mary then bets all of her 100 votes. This impresses the others, so they try to convince Ryota to ditch Mary. Mary tells them off, however. Due to knowing what cards the sisters must have, she could prevent them from defeating Ryota.

Mary and Ryota are invited to the auction. In the second half of the auction, all of them discuss what they should do. Ryota tries to calm them down, but Mary tells him to shut up, because he has no votes anyway.

Fanon
Ryomary is not nearly as popular as other ships involving the two, such as Meariri, Yuryota, and Yumary. The ship is also disliked by many fans, due to the fact that Mary was initially very cruel to Ryota. Many fans may also question if Mary would ever agree to be in a relationship with a man. Ryomary may also be unpopular because of Ryota's canon feelings for Yumeko.