Zichen's been a bit morose of late. Though he hasn't mentioned anything specific, it's in the air around him, easily detectible by someone who knows him well. Rather than waiting for Xingchen to inquire, he deicdes to bring it up on his own.
"Xingchen, have you... lost many people who were here?"
Not on his birthday, obv. (action)
"Xingchen, have you... lost many people who were here?"