The 29-year-old trained separately from his team mates on Saturday after nursing a back injury from the side's 3-1 win over Denmark.
But the Brazil-born defender, who also goes by the name Tulio, has declared himself fully fit as Japan bid to reach the quarter finals for the first time in their history.
"I'm okay," Tanaka said. "I just picked up a knock late in the game against Denmark and will be all right.
"You expect fatigue and stuff to build up during a tournament but I am really looking forward to playing against Paraguay."
Japan finally tamed the controversial Jabulani ball to score two stunning free-kicks against Denmark, and Tanaka feels their set-piece prowess could also undo Paraguay.
"They will be trying everything on to rile us," he continued.
"Every goal is so much more precious now in this knockout stage and it is important we try to get our noses in front first.
"One thing we will have to try and do is vary our set-pieces to surprise them."