Mari and Basil's ages are a topic that often comes up among fans of 'OMORI', especially since their dynamic is so central to the story. From what I've gathered, Mari is older than Basil, though the exact age gap isn't explicitly stated in the game. Based on contextual clues—like their roles in the friend group and how they interact—Mari seems to be around 16-17, while Basil is likely 12-13. The difference makes sense given how Mari takes on a nurturing, almost big-sister role toward him.
What's really interesting is how their age gap influences their relationship. Mari's maturity contrasts with Basil's innocence, and that contrast is part of what makes their bond so touching. The way she looks out for him adds layers to the story, especially when things take a darker turn. It's one of those details that makes 'OMORI' so emotionally resonant—you feel the weight of their connection, even without hard numbers.