Big Man Japan

An eccentric man living alone in a decrepit house in Tokyo periodically transforms into a 100-foot tall giant in order to defend Japan against similarly sized monsters.
Daisato, a second-rate, third-generation superhero, annoys his neighbors with the noise and destruction he causes on the job. But a heroic public image is the least of his concerns. Besides defending Japan from bizarre monsters, he must deal with an agent seeking to brand him with ads, a superhero grandfather with Alzheimer's and a family embarrassed by his incompetence.