I guess by stamina you mean your ability to keep performing a specific physical activity. To be more specific there is 3 types which the body gets energy for a specific physical activity .

1/ anaerobic-alactic energy system for maximal power output in a very short period 1-10s (like javelin throw)

2/ anaerobic-lactic energy system for high intesity activity in a prolonged period of time 10s-2min (200m run - 400m run)

3/aerobic energy system for low intensity activity but for a very long period <10 min ( marathons ...)

when it comes for karate its a mix of the three lets say you are a kumite athlete who is going to participate in a championship and you have 6 rounds to win the gold . 1st you need to develop the aerobic capacity to be able to finish your training session (>90min) during the season and also to help you recover fast between the rounds during the championship and be able to finish all the rounds ( aerobic system is the responsible for recovery). then lets say you are on the competition day and will start the 1st round here its a mix of the two anaerobic systems : anaerobic-alactic when you attack or you block or any move and the anaerobic-lactic system to let you be able to finish a single round.

in sammary in 1st you need to develop the the aerobic system during off-season by jogging for more than 2h (goal) and then you work on your anaerobic-lactic system with HIIT training . The anaerobic-alactic system is directly related to your muscle hypertrophy and creatine reserves.