Answer:
Video.
Step-by-step explanation:
Medium is the electronic mode by which a person can learn or know about anything. This medium involves the use of recordings, playbacks, or a display of any moving visualization.
In the given scenario, Kira wants to show her brother how to sew. And though this can be done by teaching as in the description of the step-by-step process. But the best form will be to make him watch a video of how sewing is done which will ensure that he sees and be able to capture the movements and process in a detailed manner.
Thus, the type of medium to be used is video.