Tension is mounting around CenturyLink Field as the 12th Man and 49ers fans engage socially.
At Fuel in Pioneer Square, 49ers fans chanted at Seahawks fans, who returned the jeering with their own 12th Man energy.
"I've been here before and it wasn't this bad," said 49ers fan Catherine Tate. "But they're good now so they feel like they have some 'umf' behind their team."
Fuel will charge 49ers fans a $12 cover tomorrow while the 12th Man will walk in free.
"We're very passionate about the Seahawks here at Fuel and in Seattle," said Fuel owner Mike Morris. "We want to see the Seahawks whoop up on the 49ers tomorrow."
Morris turned up the music at Fuel in order to quiet fans and lower tension. He calls the rivalry "good fun" and wants to make sure it stays that way.