The Libertadores Cup holders are expected to face European champions Barcelona in this weekend's final, barring the unthinkable in Barca's semi-final against Qatar's Al Sadd on Thursday.
Neymar struck fear into Reysol every time he touched the ball. The 19-year-old put Santos ahead after 19 minutes, curling a superb, left-foot shot into the top corner from 25 metres.
He had already hit the post as Santos, crowned South American champions for the third time in June almost 50 years after Pele led them to back-to-back titles, surged forward from the start.
Strike partner Borges smashed in a second goal from the edge of the box in the 24th minute as Santos flexed their muscles and the floodgates threatening to burst open.
Defender Hiroki Sakai threw Reysol a lifeline with a powerful header nine minutes into the second half, until Danilo bent a breathtaking free kick around the wall in the 63rd minute to slam the door on the J-League title holders.
Substitute Ibson rattled the crossbar as Santos came close to a fourth goal. On such form, the Brazilians will be hard to beat, even by Barcelona, who are chasing a second Club World Cup title in three years.
Barcelona's semi-final against Asian champions Al Sadd and Sunday's championship match both take place in Yokohama.