A half year after he got out of prison, Daniel Tang has made a habit of going back. He waits in spare, crowded corridors. He greets familiar faces among the fellow visitors and guards. He brings books, postage stamps, writing paper and packets of M&M's.

Tang is visiting people like him who were imprisoned for their role in the pro-democracy street protests that rocked Hong Kong in 2019. He travels three hours, round-trip, for a 15-minute chat through a thick plate of glass, sometimes with a total stranger. He summons a cheery, chatty demeanor, when he feels anything but.

"You owe them your best face,” he said. "If you’re not feeling right, don’t even bother going.”