What are the requirements for language school visa

Hi everyone, i passed jlpt n5 , and i got accepted in a language school for October 2026, its called kanrin academy in yokohama, i was told that my sponsor has to have 2.5 million yen in his bank account, but we dont have that much just laying around, it is invested in stocks, he is going to get the money in bank account. Now i want to know ,will it be suspicious to suddenly deposit the money, and by which month should i deposit it to be safe.. it is for October 2026, and i dont know anyone in japan,if anyone is going to the same area and is interested in talking ,please feel free to massage me.