Question: when does naruto start to learn sage mode?
Answer: He finds out in episode 152 but its not till episode 154 where Fukasaku takes Naruto to Mount Myoboku to train in Sage Mode. In ep 154 Naruto learns the risk of death and basics of Sage Jutsu. In ep 155 Naruto utilizes toad oil, gets whacked multiple times if he has any notion whatsoever of becoming a toad.