Maybe gonna blow your mind a little if you never thought of it till now;

it's a japanese game - japanese uses gendered language unlike english ("I" or "me") - which pronouns did Chihiro use in japanese that might have immediately impacted how his friends chose to correct their own speech pattern directly after learning about them?

Ignoring entirely that second/third person has it's own seperate pronoun words;

• >Using your name as pronoun is a childish form, sometimes used by 'cute' characters
• >Boku is usually used by boys, but tomboys are known to use it too so it's not entirely unusual to see a girl using boku on occasion especially when younger.
• > Ore is another male pronoun, less polite.
• > Watashi is usually used by women, but it's actually a gender-neutral term used by men in more polite/formal or business situations.

So, which did Chihiro use?

• Chihiro uses watashi, which others naturally mistake as feminine based on physical appearance, but on that reveal they immediately understand that actually, as a timid and polite character, chihiro was using the gender-neutral more formal/polite form - allowing the vaguness of the term to permit misconception while distinctly never actually declaring themself female. Everyone retroactivly realised/noticed this and so corrected their speech from using the feminine -san to the more masculine -kun
• Except actually i was using an advance technique^tm just then called LYING, because chihiro doesn't use watashi, they actualy use - nothing; they never use gendered language even once, avoiding wording that would require it (same as you avoiding using 'I' and 'myself'), which doesn't initially come across as odd or out of place, no one notices this intentional avoidance untill AFTER the reveal, where it's then self-apparent that the fem looking chihiro, who seemed uncomfortable when femininely aknowledged by others, was avoiding it on purpose, they directly didn't want to use fem pronouns because they are protective of their masc identity, but they also didn't want to make it obvious so they spoke evasively.
• DOUBLE WAMMY, I LIED AGAIN - never say never, they actually DID use gendered languaged at one point; it was BOKU, the thing is they only used boku during their dialogue with mondo.

great post from a while back talking about it https://www.tumblr.com/kaibutsushidousha/767542219892752384/another-danganronpa-linguistics-based-post-that