Inzaghi injured his knee in a friendly match against local Japanese side Kashima Antlers last Sunday and was a major doubt for Italy's opening Group G game against Ecuador.
But the AC Milan forward has made much quicker progress than the seven to 10 days' recovery period he was given by Italy team doctor Andrea Ferretti.
The low-key training game saw Italy's reserve players win 7-0 against a selection of youth players from local J-League club Vegalta Sendai.
Inzaghi played without any problems but Italy coach Giovanni Trapattoni looks to have already settled on the strike pairing of Francesco Totti and Christian Vieri.
Italy play Ecuador in their first match on 3 June before also playing Croatia and Mexico.