Niwa and Maharu Yoshimura have been frequent doubles partners starting in 2016. The pairing first rose to prominence at the 2016 Summer Olympics Men's Team Event where the pair contributed to Japan's silver medal. At the 2017 Asian Championships in Wuxi, the pair reached the semifinals before losing to Fan Zhendong/Lin Gaoyuan. At the 2017 World Table Tennis Championships Men's Doubles event, the pair won a joint bronze medal. The following month, at the 2017 World Tour Japan Open, Niwa/Yoshimura reached the finals before losing to Ma Long/Xu Xin in three straight games.