This happened in 2014, it was my first time in Japan and I travelled with a tour group with my parents.
We were heading down towards Gotemba premium outlet in japan, after staying at a hot spring nearby, and along the way, we smelt something burning in the bus, but the weather was cold and we wrote it off as a misidentification.
A couple of minutes later, the bus pulled up to the side of the road and stopped at the side, being a Singaporean tour bus, everyone started asking each other what was happening. Which no one had the answer to. The tour guide stepped up and tried to pacify us before giving us the news, we were stranded, the bus broke down in the middle of the highway, the heaters wouldn't work too so we had to just endure the cold.
The bus opened up and a majority of the passengers stepped out of the bus (In fact all), after stepping off the bus a chill wind blew past and that's when the realisation hit me. I have to pee, desperately. I looked around and there was nowhere to go, no place for me to pee. On the other side of the bus was a steep drop, with railings so that wasn't an option. The tour guide informed us that the bus that will be coming to pick us up will be arriving in 30 minutes, the journey to Gotemba would be another 30 minutes. So began the longest hour of my life.
30 agonising minutes passed before the bus finally arrived, everyone shifted to the other bus while the drivers helped to load up the luggage. After that was settled everyone settled in and prepared to move off. Just as the bus was about to move off, one careless family realised that they were supposed to bring everything along and stopped the bus before alighting to bring their things on board.
The agonizing journey ended at Gotemba and I ran full speed to the toilet only for everything to be occupied. I had to wait again until I finally managed to release the pee I had held in for so long.