Well, based on my experience, they donīt have much ads on TV in Japan.
When we got back to our hotel at night, I turned on the TV and some japanese drama was playing, I decided to watch it until Iīd fall sleep. One thing I noticed unlike my own country, they
BARELY have any adds at all. You donīt have time enough to make yourself a snack or go to the toilet!

They would play about two commercial clips which were around 15-20 seconds each and then back to the show.
This makes sense if you think about it though. Given how watching tv is seen as "wasting time" in Japan, and most people only watch it when they come home from work before they sleep or something similar, making tv adds wonīt really increase the company's market values.
Instead, walking around in the city's, sitting on trains, youīll encounter
ALOT of advertisement. Since lots of people take the train and walk around in the city everyday(believe me its crowded xD), they chose to use the adds there instead, thatīs why you see "tv screens" on big building walls advertising about a new product.
So basically, Japan donīt have many adds on tv, youīll see them while sightseeing in the towns instead
