Situational irony arises out of Oscar’s relationship with Ybón, a prostitute he meets in Santo Domingo. In Book 3, Oscar explains his love to Yunior: 

So this is what everybody's always talking about! Diablo! If only I'd known. The beauty! The beauty!

The love Oscar feels for Ybón is the truest love in The Brief Wondrous Life of Oscar Wao. With Ybón, Oscar finally understands “what everybody’s always talking about,” and he can finally see beauty. 

The purity of their relationship is ironic on a few levels. Ybón is not an expected match for Oscar. She is much older than he is, and she’s a prostitute. As such, Ybón is considered to be at the bottom of society, looked down on by many. Oscar has not previously exemplified the version of masculinity that might typically be associated with seeing prostitutes, and he has not had physical relationships with women before. But Oscar’s rejection of macho-masculinity—and his ability to look past Ybón’s social status—causes him to form a sincere attachment to her. Additionally, Oscar’s relationship with Ybón is ultimately his downfall; he’s shot for continuing to see her. But even as Ybón is his downfall, she also allows him to see beauty in the final months of his life.