Hajime Moriyasu's side came within moments of a famous victory before Gabriel Martinelli struck deep into stoppage time to hand Brazil a dramatic win.
The Asians had taken an early lead through Sano's first-half goal and looked capable of causing a major upset for much of the contest.
However, Casemiro restored parity for the Selecao before Martinelli's late winner ended Japan's brave World Cup campaign cruelly, leaving Sano disappointed despite the team's spirited display.
"I think results are everything, and I'm really disappointed because this team shouldn't have ended like this,” Sano told media.
“But to be beaten like that at the very end makes me feel like we're not good enough, but what we've been doing isn't wrong. I think we can be proud of what we've built up.