Kurashima leads Japan's men's table tennis team, looking to break China's 16-year stranglehold on the Olympic men's singles title.
It has been 16 years since a non-Chinese man won an Olympic gold medal, when Ryu Seung-min of South Korea triumphed at Athens 2004.
China have won every gold medal since – in fact, their men have won 13 of the 16 possible gold medals since the sport's introduction at Seoul 1988. Overall, China have won 28 of the 32 medal events contested in Olympic table tennis.
Speaking to the official Tokyo 2020 website, Kurashima said he believed his charges had been able to "(maintain) the world's top level in speed and technique over the past decade or so.
"But to beat China, we also need to enhance the quality of each shot. If we can achieve this, the time will come when we will catch up with and overtake China."
Mizutani won bronze in the men's singles four years ago at Rio 2016 and the team won silver after reaching the men's team final where they faced China.
Those were Japan's first table tennis medals in men's events, marking a breakthrough for the country. At the same time, young star Harimoto was making his way through the ranks at the tender age of just 13.
Harimoto formed part of Japan's team at the 2017 World Championships, where he reached the quarter-finals a month before he turned 14.
"When the Rio 2016 Games were over, I felt a strong urge to foster Harimoto for the Tokyo 2020 Games," coach Kurashima explained. "So, when he joined the JOC (Japanese Olympic Committee) Elite Academy Program when he was in his first year at junior high school, I invited him into the national team as its youngest-ever player."
Since then, Harimoto has become the youngest winner of both an ITTF World Tour event (Czech Open 2017) as well as the Grand Finals (2018). He also won individual silver at the 2018 Youth Olympic Games in Buenos Aires. He reached a career-high world number three in January 2019, and is currently ranked number four.
"His signature strengths are his world-class powerful backhand shots, his speedy game, and his quick hits. His swift attack that deprives his opponent of any time to think is his distinctive style," Kurashima analysed.
"But to win on world stage and become the world champion, he needs more than just a strong backhand and speed. So, he is working hard to brush up on all his techniques to become an ultimate all-round player."
Harimoto is expected to be Japan's lead player in both singles and the team event.
Niwa, the inaugural Youth Olympic Games table tennis champion at Singapore 2010, is heading into his third (senior) Games. For Mizutani, Tokyo 2020 will be his fourth Games.
Kurashima believes both players see Tokyo 2020 as the "grand finale" of their respective careers, although Niwa – currently aged 26 – could still make it to Paris 2024.
"He has vast knowledge backed by a wealth of experience," the coach said of Niwa. "I believe he will produce results that exceed what he achieved in his previous Games."
Mizutani, meanwhile, is 31. "For an experienced player to remain at the top, they need to keep evolving over decades on end while younger players seek to catch up by acquiring an array of new techniques. Mizutani is one such seasoned player, continuously evolving on world stage," Kurashima noted.
"The Tokyo 2020 Games will be a gruelling competition, but I have confidence in him as a player who will maximise his potential under such circumstances."
At Tokyo 2020, the first table tennis event to take place will be the mixed doubles, which is making its Olympic debut. Japan will be represented by Mizutani and women's singles world number two Ito Mima.
"I had always thought that the two (Ito and Mizutani) would make an excellent pair, but I hadn't had any chance to try them out," Kurashima noted.
"The Tokyo 2020 Games is the first Olympic Games to include the mixed doubles event, so the opportunity was perfect for the pair. There was no other choice. Both being native to Shizuoka Prefecture, they have rapport."
"A medal, even a gold, is within our reach," he said. And Kurashima is sure that such a result would only be a boost for the four other events in singles and teams.
"The key lies in whether we can start off by gaining a gold medal in the mixed doubles to give the team an impetus in the remaining events."
(Top photo: ITTF)