According to the "Kakegurui" Fandom page, Ririka's mask serves as an emotional protector and support mask of sorts. When she was a child, Ririka's parents tried "erasing" her existence by forcing her to wear a mask around her twin sister, Kirari. 

"When she doesn't have her mask on, Ririka is an incredibly shy and somewhat socially awkward person, who visibly has a lack of self-confidence, which makes her a complete opposite of Kirari," the Fandom page explains. But while Ririka's mask — which is fitted with ominous black eyes and a smile — is meant to hide and shun the character, many fans have grown extremely fond of it over the years. 

"Ririka's mask makes me laugh so hard," tweeted @Bakabami. Back in December, user @RellFGC noted how relatable Ririka's behavior was while donning the facial covering. "Ririka gets knocked down, has her face revealed, puts the mask back on and goes right back to being a mystery like nothing happened," the user said. "This is me. Light flashes of vulnerability, you see who I am for a moment, then back to thug mode."

It's currently unclear when Season 3 of "Kakegurui" is expected to drop on Netflix, or if it's even be renewed for an another run.