[3] At the Tokyo event of the 2018 FINA Swimming World Cup, Namba won a silver medal in the Women's 400m freestyle, and a bronze medal in the 800m freestyle.

[4] In the 2019 World Cup, she took bronze in the 400m freestyle.

[4] She placed second in the 800m freestyle at the 2019 FINA World Junior Swimming Championships.

In the 400m freestyle qualifying competition, Namba was ahead of the field for most of the race, but lost to Waka Kobori with a time of 4:06.36 against Kobori's 4:06.34.

[5] Namba won the 800m freestyle qualifying final in 8:26.61, with Kobori second with 8:26.67.