Public calls for Tokyo Gov. Yoichi Masuzoe to step down grew Tuesday despite his apology a day earlier and a pledge to refund some of the ¥4.4 million in "improper" political spending he is responsible for.

But Masuzoe appeared determined to stay in office, and indeed forcing him to step down may prove difficult given the size of the loopholes in the Political Funds Control Law, experts say.

Attention has now shifted to whether the Tokyo Metropolitan Assembly will set up an investigative committee with the muscle to pry Masuzoe from his position, they say.