Police said they received a report at about 2.50am on Sunday from a 25-year-old man that the 1,000 sq ft shop in Chung Mei Centre on Hing Yip Street, Kwun Tong, had been ransacked.
He also found that more than 10 security cameras had been sprayed with red paint.
An initial count indicated that about three boxes of Pokemon cards were missing.
Officers are searching for a suspect described as about 1.7 metres (5 feet, 7 inches) tall, of medium build, wearing a surgical mask, a yellow safety helmet, a black jacket and dark trousers.
Investigators believe the thief entered from a back alley on Hing Yip Street, climbed scaffolding set up for building repairs, reached a platform and then forced open window grilles to gain entry.
The shop’s main door showed no signs of tampering.
