world ranking as of July 2012 but has achieved ranking as high as 5th. She is now the best female table tennis player in Japan after managing to overtake Ai Fukuhara in rankings. She reached the semi-finals of the Women's Singles at the London 2012 Olympics but lost out to eventual gold medal winner; Li Xiaoxia of China. In the bronze medal play-off, she lost out to Feng Tianwei of Singapore. She finished an overall 4th position. This was her first ever Olympics participation and despite her young age of 19, she was seeded no. 4 at the Women's Singles Event. She is also the first ever Japanese to have reached the semi-finals of the tournament. At the Women's Team Event semi-finals, Kasumi Ishikawa helped Japan to overcome Singapore by defeating her quarter-finals opponent in the Single's, Wang Yuegu in three straight games. In the third Double's game, she paired up with Sayaka Hirano to overcome Wang Yuegu and Li Jiawei in three straight games as well. The wins together with Ai Fukuhara overcoming Feng Tianwei in the first game brought Japan to their first table tennis finals in the Olympics in three straight matches. However, Japan failed to beat China in the finals but got their first ever silver medal in table tennis. She won bronze with the Japanese Olympic team in Rio de Janeiro 2016, beating together with Ai Fukuhara and Mima Ito on her side the team from Singapore. She also represented Japan in the women's singles event, where she crashed out of the tournament after suffering a cramp in her leg, losing 4–3 to North Korea's Kim Song-i in their third-round match. At the 2017 World Table Tennis Championships held in Düsseldorf, partnering compatriot Maharu Yoshimura in the mixed doubles event, Ishikawa and Yoshimura progressed through to the final, beating the combination of Fang Bo and Petrissa Solja in the semi-finals, and overcame the Taiwanese pair of Chen Chien-an and Cheng I-ching 4–3 to win the first title in this tournament. It was also Japan's first mixed doubles gold medal after 48 years. In January 2020, she was announced to be part of the women's table tennis team for the 2020 Tokyo Olympics, together with Ito Mima and Miu Hirano. Furthermore, she will be making her third appearance in the Singles category with Ito Mima. 2021 Ishikawa defeated Miyuu Kihara in the semi-finals and Mima Ito