Ri is a pronoun that some people use to describe themselves instead of saying he or she. You know how when you talk about yourself, you say "I"? Well, some people choose to say "ri" instead.
It's similar to how some people prefer to be called a different name or use different pronouns because it feels more true to who they are. It may seem different or strange to some people, but it's important to respect others' choices and use the pronouns they prefer.
By using the correct pronouns, you show that you care about and respect that person for who they are, and that's a really nice thing to do.