Pros
Easy way to get a visa sponsorship to live in Japan.
Cons
Terrible pay for one and they have pretty bad contracts that manly help themselves, but disadvantages you as an employee or contractor. if you pick the employee contact you'll get paid 800 yen per hour which is very low and is under minimum wage in Tokyo. whatever you do, don't let them give you a place to stay. As for the contractor role you'll get better pay but if the staff or students don't like you they'll cut your lessons and give them to another employee or contactor. they'll mostly give the lessons to an employee because he is cheaper and by immigration law he is guarantied work.