Maximum Hours to study Nihongo in Japan?

If I plan to study and learn Japanese Language in Japan, is there a limited hours a day I can study it? Because while searching some information regarding studying there, I keep reading about 4 hours a day but I'm not sure if it's for studying or work part-time only.

Why would there be a limit? Where did you hear such an odd thing?

There are no limits or visa restrictions for the time you spend studying, but most Japanese schools generally have around 4 hours of lessons per day for each class. There may possibly be some schools that have longer lessons, but 4 hours per day can still be quite intensive for some people.

The reason why Japanese language schools have 4 hours a day program is because "4 hours a day, 5 days a week" of classroom lessons are considered "full-time study" for language schools, thus students enrolling in this full-time program is eligible for Student visa.

Note that if you have 4 hours of classroom hours at school, you will need to study before and after the classroom lessons, so you will be doing a lot more "studying" than just the lessons :)