Made-up Settings

This is a story about Yachiyo getting caught by Iroha because her sexual arousal peaked so high from the Emotion Sensing that she ended up having a brain orgasm.

Tsukuyomi's Emotion Sensing doesn't just detect feelings; it actually triggers physical reactions on the VR avatar to represent those emotions.

For example, if you feel "Sad" (Emotion), a "Tears" (Reaction) emote appears. If you feel "Panic" (Emotion), "Sweat" (Reaction) appears. These reactions are reflected in real time.

Therefore, if you feel sexual arousal intense enough to cause a brain orgasm, it will be reflected on the avatar too. (Convenient Interpretation #1)

And since Yachiyo is definitely the type of girl who can have a brain orgasm (Convenience #2), so that's how it goes.