Sanji's emotion continued to be revealed in Chapter 841. There will be definitely more shocking and devastating discoveries for our calm and cool hero Sanji.
Sanji, as what was revealed from the Chapter 840, is the 3rd son of a powerful, royal family of Underworld killers from the Germa Kingdom. However, according to his father, he is the most humane and weakest compared to his siblings. Sanji's being warm among the brood was evidenced when he defended head chef Cosette from his brother Niji, after an argument which made Niji angry and attacks Cosette during a meal.
Fans are starting to uncover the truth and the evil side of the Vinsmoke family as it was revealed that Jajji Vinsmoke, aside from being the king and supreme commander of the kingdom, he was also a scientist. Because of his highly advanced skills, he used it to clone people so he can use them as his army to fight in a battle. This is most likely the reason why Big Mom Pirates and her army wants a coalition with the mighty clan through the marriage of Sanji and Charlotte Purin.
Meanwhile, readers can expect more revelations about Sanji's childhood in "One Piece" chapter 841, where Sanji had agonizing moments under his strong brothers. They were practiced and forced to go through excruciating and difficult training but couldn't keep up with his elder brothers' abilities.
"Black Leg" Sanji's identity may be revealed in "One Piece" chapter 841 - that he can a clone or some sort of a high specialized human developed and created by science. There are speculations that due to this possible horrible discovery, Sanji might awaken his true power and strength and that he will challenge his siblings and possibly that of his father. Based on a Reddit forum, the scans for chapter 841 will probably be out Sept. 29.