He said in these economic times it had simply become too hard for his independent shop to continue.
"It's difficult trading times for retail at the moment."
Mr Lee said Serious Fun had been in Rotorua for about 20 years, eight under his ownership, so it was sad to see it go.
However, he was pleased it had been bought and would continue to trade, rather than sit empty.
The Backdoor Surf owner, Geoff Hutchison, said the closing-down sale would run for a further six weeks or so.
He said the shop would then close briefly for a refit before reopening as Backdoor Surf, joining nine others throughout the North Island.
Mr Hutchison said he seized the opportunity to launch in Rotorua when Serious Fun became available as it was a lot easier than starting from scratch, adding it also made sense geographically with most of their stores in nearby Hamilton and Mount Maunganui.
He said he was "reasonably confident" there was a market in the city, saying Rotorua shoppers could expect more New Zealand brands, more "current and cool" labels and more surf and snow products when they reopened as Backdoor Surf. He confirmed the Serious Fun staff had been kept on.