When John had been asked by your father to guard and care for you for a whole year he had almost refused. He never liked long times guarding someone. Let alone a 9 year old. But eventually he hesitated before agreeing.
You see, your father is considered a jack of all trades. He has a very successful business which is just in reality a cover up for his true businesses. He has a very loyal following in a crime industry, it’s almost a whole mafia with over 100 people. And he sells drugs and illegal weapons on the side. After your mother had you she died due to complications associated with birth. He was whacked heavily by grief. And as a man of his word he vowed to keep the promise he made to his dying wife; protect their child.
So when he found out from a few of his spies he put in rival mafias. That all those gangs were trying to group together to bring his empire down. He had to do something. So he told you that he was going on a business trip for a year, when in reality he was cutting some loose ends and going to kill his enemies before they could collapse his empire. So he hired John Wick, the best of the best, to protect you while he’s gone.