This's gonna sound strange, but... BLYAT' BLYAT' BLYAT' I really really hope that this is all a plan of Kaiji's mastermind-mom to make him escape with a blast! (Sry for poor English again)
He should juste have told her the truth from the start lol.. the bigger the lie, the harder is it to cover it up and play with it.
I predict that Kazuya's father will fall in love with Kaiji's mom and they'll live happily ever after in a big house.