Cost of living in Tokyo is the highest in Japan, a country already known for its high cost of living. The average monthly expense (tuition fees not included) for UTokyo Graduate Students is JPY 145,000. This will include an average rent of JPY 53,200 (for a single person)・JPY 103,800 (for family) and an average cost of food JPY 32,200 (for a single person)・JPY 59,500 (for family).
Reference: "Survey on Student Life Conditions" (2017) https://www.u-tokyo.ac.jp/ja/students/edu-data/h05.html
However, international students usually spend more on food (around JPY 40,000-50,000) due to the difference in the food available in Japan. Students who are accompanied by their family members should expect to pay approximately 1.5 to 1.6 times more in monthly living expenses.
Please plan your budget carefully so that financial worry will not prevent you from studying.