When Soren said those words Ace and Sabo gave him a weird look, Luffy on the other hand didn't care and wanted to continue playing.
[What do you mean "You came here to watch us" are you guys some kind of pedofiles?]: ace
When Soren heard Ace's comment he thought about his words only realizing now that, coming out into the woods where 3 little boys would play and tell them that he was there to "Watch" them was a bit weird. Soren then looked back at them and said.
[I came here to help you guys become stronger, and by doing so I need to watch how you guys train]: soren
Luffy who was originally just standing around waiting for something to happen then spoke up.
[Train? We are just playing, what would we be training for?]: luffy
[We are training to become the best pirates in the world you idiot]: ace
Ace hit Luffy over the head when he said that and reminded Luffy of why they came here every day for the past couple of years.
[Luffy, we need to become stronger so we can meet Shanks again]: ace
When Luffy heard Ace's sentence he remembered that he could only meet Shanks if he became a pirate and went to the Grand Line, there he would find the One Piece and meet Shanks again.
[Yeah, I will be the Pirate King!]: luffy
Luffy has always wanted to be a pirate but he almost forgot when he would train with Ace and Sabo every day because to him they were just playing around until they could become pirates. Soren saw Luffy's realization and thought that Luffy was really just and idiot, he then decided to let the cat out of the bag.
[Luffy… You want to become the Pirate King and meet Shanks again, right? Well I was instructed by Shanks to help you achieve your goal by being your mentor]: soren
When Luffy heard Soren's words he froze up and thought for a moment.
[You know Shanks? Also, I don't need help… I will become the Pirate King on my own]: luffy
Soren saw Luffy's determination while Ace was pondering over the words that Soren told Luffy, and Sabo was left out of the whole conversation only there if a fight broke out he would be needed to help.
[Yes, I know Shanks… I was a member of his crew, I left because I have a wife now… His last request before I left the crew was to watch over you and make sure you grow into a fine pirate]: soren
Soren told Luffy everything that Shanks wanted Soren to do and left nothing out, Luffy was standing there with tears in his eyes due to the fact that Shanks really did care for him.
[*Sniff Sniff* Then it's settled… You will teach me!]: luffy
Ace wasn't too quick to accept Soren as he felt that he could be lying to Luffy and he asked.
[If you really are a member of Shank's crew then show us how powerful you are]: ace
Soren looked towards Ace and saw his determination to see just how powerful Soren really was, Soren then opened the system and bought 3 cheap iron swords that didn't even cost 10 system points and opened his inventory letting them drop out onto the ground. As the 3 boys saw the Iron swords drop out onto the ground from nowhere they were stunned only to be awoken by Soren's next words.
[Pick them up then attack me with them]: soren
The 3 boys felt Soren was an idiot to let 3 people attack him with real swords and quickly Sabo spoke up.
[You do know that these are real swords right? If we accidentally kill you then what?]: sabo
Soren heard Sabo's complaint and said as he grabbed a blindfold from his inventory.
[Oh? Then I will deserve to die, I spent 3 days blindfolded with Shanks whole crew attacking me, they barely left a scratch on me]: soren
Sabo's mouth dropped at Soren's words and felt that he was lying, he then walked forward to pick up a sword as Soren finished tying his blindfold.
[Okay!... Now let's sta-]: soren
Soren couldn't finish the words before he dodged a swords strike and said.
[I didn't say start yet, did i?]: soren
Sabo who had just tried to strike Soren with the sword was stunned to see that even when Soren wasn't ready he still dodged the sword.
[I was just testing your claim, that's all]: sabo
Soren smiled at Sabo's words and then stated.
[If you guys and manage to land a strike on me then you all can depart now to become pirates, am I clear?]: soren
[But Shanks said-]: luffy
Luffy couldn't finish his words before Soren cut him off.
[Shanks is overruled by me, if you can land a strike I will take you to Shanks personally]: soren
Luffy lit up at Soren's words and then said.
[But wait… I don't know how to use a sword]: luffy
[Then use your fists, if you can't use your fists then use a gun, if you can't use a gun then use any form of attack]: soren
Soren had sat there the whole time explaining that they could use anything that they felt comfortable using, Sabo then switched to his staff, Ace and Luffy both ran at Soren with their fists.
[Take this!... Gomu-Gomu Pistol]: luffy
Luffy then stretched his hand back super far and shot it forward like a pistol, Soren dodged it with no effort at all while Sabo was still trying to whack Soren like a pinata.
[Good, Good… You guys may be teachable after all]: soren
Soren spent the rest of the day letting the 3 boys attack him, Soren even at one point started having conversations with Misha. By the end of the day Ace, Sabo and Luffy were tired out and were ready to go home, but before they could leave Soren called out to them.
[Hey! I have a gift for all of you]: soren
[Really! Where? Where? Gimme gimme gimme!]: luffy
Luffy had shot up and ran towards Soren for his "Gift" Soren then opened the system and bought a bunch of weighted clothes that weighed about 100kg total and handed one set to Luffy and the other 2 sets to Ace and Sabo, he also bought one for himself that he would increase gravity on later.
[What is this? Why is it so heavy?]: ace
All 3 of them could barely lift the clothes that were handed to them and asked Soren what they were.
[These are weights… They weigh about 100kg each and will help you train, form today on you will wear these clothes during training]: soren
The 3 boys looked like they just died as Soren said that they would wear these during training, Soren then dismissed them and started to head home.
[Hey!... Anybody here? Hello! I'm stuck under these clothes!]: luffy
Poor Luffy had gotten trapped under the weighted clothing that Soren gave the 3 and he spent the rest of the night there.