especially after finishing the most recent volumes of 'Classroom of the Elite'. His smile is basically a social weapon, and it's terrifying how it operates on different levels. For his classmates, especially early on, that placid, gentle smile becomes a kind of default expectation. They see a quiet, harmless guy who's just happy to help. It lulls them into a false sense of security, making them underestimate him. They trust the facade because it's consistent and non-threatening.
But for someone like Kei Karuizawa or even Horikita later on, the smile becomes a point of distrust precisely because they've seen glimpses of what's behind it. When he smiles after manipulating a situation perfectly, it doesn't reassure them—it confirms their suspicion that every emotional display is calculated. The trust shift isn't about whether they believe he's good; it's about whether they believe his emotional output is genuine. His smile rarely signals happiness; it signals that a plan is proceeding, and that distinction is what alters trust dynamics. For a character like Ryuuen, the smile is an outright challenge, a taunt. It erodes any possibility of straightforward trust and replaces it with a wary, competitive respect.
In the end, I think Ayanokōji smiling makes other characters trust his competence and his predictability as a chessmaster, but it completely obliterates trust in his humanity or his alignment with their own emotional interests. They learn to rely on the result of his actions, never on the intent implied by his expression.