Freshly cut onions often cause a stinging sensation in the eyes of people nearby, and often uncontrollable tears. This is caused by the release of a volatile gas, syn-propanethial-S-oxide, which stimulates nerves in the eye.
So that's why you cry when chopping an onion.
Huh. And this whole time I thought it was because killing a perfectly good onion fills me with sadness at the loss of life.
'Cept Shiho is basically the crux of everything Ann does, she never fails to instantly turn the topic about Shiho and the last half of Ann's social link is also about Shiho.