The boys’ team of rugby player Franc, American footballer Reef and gymnast Sol are in Japan to learn their national sport of sumo wrestling. Watched over and cheered on by presenter Karim Zeroual, at the end of the week they will be competing in a sumo wrestling tournament against top young locals. Today, head coach Sensai Inahara wants to test the boys’ leg strength – essential if they are going to have a chance of winning a wrestling match. To do so, he is taking them to the mountains to scramble up rivers and squat under freezing cold waterfalls. Meanwhile, Karim is getting wet in a totally different way – trying and failing to work out how to use one of their high-tech toilets.