Anthony Seric smacked a powerful long-range shot to make it 3-0 in 82nd minute.
And Goran Vlaovic completed the scoring in extra-time with a delightful chip over the
Croatia dominated the match, giving Toyama virtually no scoring opportunities.
Star striker Alen Boksic was resting an abdominal injury, in the hope that he will be fit in time for the opening match against Mexico on
3 June in Niigata.
There were mixed fortunes for two of Croatia's Group G opponents on Sunday.
Ecuador saw striker Agustin Delgado return after injury.
But the South American side could only draw 1-1 with Kyoto Purple Sanga in Kobe after Alex
Aguinaga found the net.
Mexico secured a 2-0 victory over Tokyo Verdy.
Goals from Braulio Luna and Francsico Palencia gave them a comfortable workout as they proved too strong for their J-League opponents.