The new Barcelona acquisition turned in a superb display to inspire the Seleção to three points and keep their hopes alive for a third consecutive Confederations Cup title
Goals from Neymar, Paulinho and Jo ensured that the Seleção maintained their unbeaten record against the Asian nation with a convincing performance to alleviate some of the pressure on Luiz Felipe Scolari's shoulders.
There had been much debate as to whether new Barcelona signing Neymar could rise to the occasion and he provided the hosts with the dream start with a sumptuous strike after just three minutes.
The 21-year-old ended his nine-game streak without a goal for club and country with a stunning half-volley into the top right corner after Marcelo's cross had been deftly cushioned into his path by the chest of Fred.
Japan almost struck back immediately when Keisuke Honda tried his luck from distance but his fierce free kick was palmed to safety by Julio Cesar.
The CSKA Moscow midfielder proved a constant thorn in the Seleção side and he forced the Queens Park Rangers shotstopper into another save on 18 minutes from the edge of the box after jinking inside the challenge of David Luiz.
The partnership of Dani Alves and Hulk down the right wing was causing the Japanese defense problems and the pair combined excellently on 22 minutes but the Zenit St. Petersburg forward's dangerous low cross was crucially hooked clear by Japan captain Makoto Hasebe.
The same two players combined again five minutes before the break with Alves feeding Hulk on the right-hand side of the box. The forward cut inside the challenge of Yuto Nagatomo onto his preferred left foot before thumping a ferocious drive into the side netting with Eiji Kawashima scrambling.
The Standard Liege goalkeeper was called into action soon after as he produced a fine finger-tipped save to prevent Fred's low drive across goal after the striker had been picked out by Neymar's inch-perfect cross.
The Samurai Blue came out of the blocks quickly after the interval but it was the hosts who doubled their advantage three minutes into the second half. The relentless Alves drove forward from defense before his fizzing low cross was controlled expertly by Paulinho, whose low shot somehow squirmed under the body of Kawashima.
Brazil's performances have come under scrutiny since the re-appointment of Scolari but the boys in yellow appeared solid at the back and irresistible in attack, throwing down the gauntlet to the rest of the world that they are serious contenders for the World Cup next summer.
Alberto Zaccheroni's side really should have pulled a goal back on 50 minutes when Hiroshi Kiyotake's teasing low cross found Shinji Okazaki in the area, but the Stuttgart forward inexplicably steered his effort the wrong side of the post.
Ryoichi Maeda was introduced in a bid to add some attacking steel to Japan's play and the striker nearly reduced the deficit on 72 minutes when he latched onto a loose ball in the Brazil box before swivelling and forcing Cesar into a smart stop with his low effort.
The boos did ring out for Scolari however when he opted to withdraw Neymar from the action, but with games against Italy and Mexico to come, the 64-year-old's decision was understandable.
Late substitute Jo added gloss to the scoreline in stoppage time when he swept home from Oscar's pass after a devastating counter attack to cap a convincing display from Scolari's side.
Brazil could secure progress to the semifinals with victory against Mexico on Wednesday evening whilst Japan looks to get its first points on the board when it faces Italy.