I’m going to a Japanese language school for 6 months with a student visa next year. Will the student visa be exactly 6 months? Or is it actually longer?

I'm planning to go to a Japanese language school next year. I will enroll the school for the April term for 6 months. I was wondering if the duration of the student visa will be exactly 6 months or if it's longer than that. I'm asking this because I don't know if they take into account the time it takes you to settle in the country and if they also give you some extra weeks or months to leave the country after one finishes the school. I read that some people after finishing the school they had 3 months to leave the country, so I guess their visas were longer than the time they were studying at the school. Can someone clarify this for me?