Hangin out with Celeste and she said something that sounds like a SDR2 refernce

[Saiche]

She said she played against a silver haired boy said to have the devil's own luck. Nagito?

[Protocol27]

Can't think of anyone else but Nagito.

[Shy Monkeys]

It's a reference to a manga from what I hear. I think it was called Akagi.

[Phantron]

All the freetime events where she talked about beating other gamblers are references to other gambling mangas. They're your typical invinicible guys with crazy luck but since Celeste is so awesome so she beats them anyway, sometimes without even knowing what the rules of the games are!