Joh 6:14, 15  "When the people saw the sign that he had done, they said, "This is indeed the Prophet who is to come into the world!""Perceiving then that they were about to come and take him by force to make him king, Jesus withdrew again to the mountain by himself." 

The people that followed Jesus up the mountain had just been fed from a few loaves and fish. When they had finished eating more than 12 baskets overflowing was left over. They began to see and understand that Jesus had great power and they wanted to take Him by force and set Him up as their ruler.
It wasn't Jesus time to reveal why He had come, He was in control and following after the Fathers leading. 

He withdrew off by Himself, the disciples were going off to go back to the village across the lake. They were in the middle of the lake when a storm came suddenly upon them. Then Jesus walked up on the water and said; "I Am here, don't be afraid." I Am the Ling of the Universe, I control the winds and the waves. They welcomed into the boat but didn't really know how He got there. It all happened so fast and they were so amazed that as soon as He was in the boat they reached shore.  

Joh 6:16 -21  "When evening came, his disciples went down to the sea, got into a boat, and started across the sea to Capernaum. It was now dark, and Jesus had not yet come to them. The sea became rough because a strong wind was blowing. When they had rowed about three or four miles, they saw Jesus walking on the sea and coming near the boat, and they were frightened.  But he said to them, "It is I; do not be afraid."  Then they were glad to take him into the boat, and immediately the boat was at the land to which they were going." 

It was the next day and the crowd was still seeking Him, to be with Him. They were traveling by land and boats to seek after Jesus and find out where He had gone. They wanted to know when He came there and how He got there because His close followers only had one boat and they knew He hadn't left with the them. 

Jesus knew that they were only seeking after the power that they thought He could provide, they weren't really wanting to know Jesus. They wanted what they thought He would give them. They wanted to be provided for materially and physically. Jesus set them straight. 
He hadn't come to give them anything but His life and to provide them with forgiveness and newness of life.  They needed to believe and receive Him as sent from the Father and the only way to be made right to the Father. He was Yahweh, He was Absolute Love. 

Joh 6:22 - 29 "On the next day the crowd that remained on the other side of the sea saw that there had been only one boat there, and that Jesus had not entered the boat with his disciples, but that his disciples had gone away alone. Other boats from Tiberias came near the place where they had eaten the bread after the Lord had given thanks. So when the crowd saw that Jesus was not there, nor his disciples, they themselves got into the boats and went to Capernaum, seeking Jesus. When they found him on the other side of the sea, they said to him, "Rabbi, when did you come here?" Jesus answered them, "Truly, truly, I say to you, you are seeking me, not because you saw signs, but because you ate your fill of the loaves.Do not labor for the food that perishes, but for the food that endures to eternal life, which the Son of Man will give to you. For on him God the Father has set his seal." "Then they said to him, "What must we do, to be doing the works of God?" Jesus answered them, "This is the work of God, that you believe in him whom he has sent." 

Wonder of wonders, they again asked Him for a sign that they could believe. They wanted Him to give bread from heaven again to verify the feeding of the feast they had received on the mountain. They wanted to see if He was as worthy of following as Moses. They wanted to know if He could do it again or it was just a one time fluke. 

Joh 6:30, 31  "So they said to him, "Then what sign do you do, that we may see and believe you? What work do you perform? Our fathers ate the manna in the wilderness; as it is written, 'He gave them bread from heaven to eat.'" 

Jesus became even more direct, "I am telling you a fact it wasn't Moses it was My Father God and I as His only begotten Son who gave your forefathers the bread in the wilderness. Moses only received what I gave Him He was under my command. I want you to know I Am the Bread from Heaven and if you receive from Me as here from My Father, you will forever be satisfied, I Am the provider of all things including sustaining your bodies." You have clearly seen Me and My identity as Yahweh, but you do not believe." They kept asking Him to give them the bread because they didn't get it they were spiritually blinded. 

Joh 6:32 - 36 "Jesus then said to them, "Truly, truly, I say to you, it was not Moses who gave you the bread from heaven, but my Father gives you the true bread from heaven.  For the bread of God is he who comes down from heaven and gives life to the world." They said to him, "Sir, give us this bread always." Jesus said to them, "I am the bread of life; whoever comes to me shall not hunger, and whoever believes in me shall never thirst. But I said to you that you have seen me and yet do not believe." 

Jesus told them very bluntly. My Father has given Me some who will hear and believe, they believe because of God's calling and choice. There is no way that those who God has placed His hand upon will not come to me in belief. This is as sure as the Word of God. 
I was sent by the Father, and I will accomplish everything as The Father and I have determined. This is the Will of God and I am able to complete His will. So everyone who sees Me as God's Son and believes in Me, they will be given abundant eternal life and I will raise them up from their graves on the last day to be with Me and My Father. 

Joh 6:37 - 40 "All that the Father gives me will come to me, and whoever comes to me I will never cast out. For I have come down from heaven, not to do my own will but the will of him who sent me. And this is the will of him who sent me, that I should lose nothing of all that he has given me, but raise it up on the last day. For this is the will of my Father, that everyone who looks on the Son and believes in him should have eternal life, and I will raise him up on the last day." 

This wasn't making the religious people happy, they began to grumble and take sides against Jesus because He claimed to be the sustenance of God Himself. He would fill them up with God, Huh! They thought they already had an in with God because of their religious practice. They said; "This Jesus is just a man, nothing special that we should listen to Him or believe the crazy things He is saying. He is Joseph and Mary's little boy. How can He now make this claim to have come from heaven."  

Joh 6:41, 42  "So the Jews grumbled about him, because he said, "I am the bread that came down from heaven." They said, "Is not this Jesus, the son of Joseph, whose father and mother we know? How does he now say, 'I have come down from heaven'?"