[2] Namigata was born in Koshigaya, Saitama Prefecture and started playing tennis when she was six years old.

[1] In September 1997, when still in junior high school, she made her first appearance in an ITF doubles tournament.

In July 2014, Namigata won her first WTA event, the doubles tournament of the inaugural Jiangxi International Open, partnering with Chuang Chia-jung.

[8] In doubles, she qualified for the 2008 Wimbledon Championships with fellow Japanese player Ayumi Morita, losing in the first round to Ekaterina Makarova and Selima Sfar.

[4] In 2017, Namigata and Chan Chin-wei received wildcard entry into the Australian Open, losing in the first round to Tatjana Maria and Pauline Parmentier.