Hey there, and welcome to Apple Support Communities tomo tnakamura,
From our understanding, during your runs the Apple Watch application abruptly stops. We can certainly understand your concern and are here to help.
We would like to ask you a couple of questions in order to get a better understanding. First, what exact version of iOS and watchOS are you currently using? We ask as the menus and options can change slightly between versions of the OS, and we want to make sure we provide the most accurate steps. You can locate this by going to Settings > General > About. Also, have both devices suffered any physical or liquid damage?
We thank you for your answers, they will help guide us to the next troubleshooting step.
Kindest regards!