Mori resigned on February 12 after saying meetings involving women tended to drag on.
Former Olympics minister Hashimoto, who competed in seven Games as a cyclist and speed skater, took on the role on February 18 and the executive board she leads will now be expanded to 45 members to allow for an extra 12 women to join.
She said that implementing gender equality was essential “in order to recover trust lost through a series of events”.
“We need to tackle this speedily and I would like to ask the board members to give us their frank opinions.”
Hashimoto said the first 12 days of her presidency had been “hectic” as the committee moves to stage the rescheduled Olympic and Paralympic Games this summer amid the coronavirus pandemic.
“On a daily basis I am faced with difficult challenges and I am spending my days in a hectic manner,” she said.
“I have been reminded of the importance of this position.”
She said a key meeting would take place on Wednesday on plans for the Games involving the International Olympic and Paralympic Committee presidents, along with Tokyo governor Yuriko Koike.
“I hope this meeting will be fruitful. There is not much time left until Games time – it is very short,” she said.
“But we need to cope with every challenge so that the Games will be welcomed by many citizens and people of the world and I will devote my utmost efforts to that.”
Tokyo 2020 chief executive Toshiro Muto confirmed later on Tuesday that the board had agreed to expand the executive board to 45 members. Seven women were already on the board, taking the total number of females to 19.
Asked whether a 45-person board would be too large to be effective, Muto said via an interpreter: “We don’t think so. We have existing board members and asking them to retire or step down is rude, not practical.
“But at the same time our target is to raise the number of women on the board to over 40 per cent. This is a challenge that we take very seriously.”