Having fallen behind to Kaishu Sano's first-half finish, Brazil improved after the break and levelled through Casemiro, but it left it late to snatch victory at Houston Stadium. 

Substitute Martinelli steered home in the 95th minute to spark wild scenes, with Ivory Coast or Norway up next for Carlo Ancelotti's side. 

Brazil started brightly, with the in-form Matheus Cunha forcing Zion Suzuki into a low stop down to his right, and Bruno Guimaraes curled narrowly wide of the far post after being slipped in by Lucas Paqueta from the resulting corner. 

Brazil went behind in the 29th minute. Sano intercepted Danilo's loose pass and drove past Casemiro before flashing a drilled shot from the edge of the box past Alisson and into the bottom-left corner. 

Vinicius Junior and Cunha both tried their luck from distance as Japan's defence frustrated Brazil's star-studded attack, with Endrick replacing the injured Paqueta at the break. 

Brazil flew out of the blocks and spurned two glorious chances to draw level, but Suzuki brilliantly kept out Guimaraes' close-range header before Casemiro's effort was somehow blocked on the line by Takehiro Tomiyasu. 

However, Casemiro was not to be denied in the 56th minute when he nodded Gabriel Magalhaes' delivery to the back post into the net

The comeback was almost complete two minutes later, but after Vinicius' dazzling run, his stabbed shot was tipped onto the post by Suzuki. 

With extra time looming, though, Brazil's moment arrived when Ao Tanaka was robbed of possession on the edge of Japan's box. Guimaraes slipped in Martinelli, whose finish just beat Suzuki and clipped in off the right-hand post.