Raised in Machakos County, Kamulu won the Pune Half Marathon at the age of seventeen, setting a course record of 1:08:37 hours. Kamulu made her international debut as a junior at the World Cross Country Championships where she finished in eleventh place and was a non-point scorer on the winning Kenyan junior women's team. Following this she began to compete in Japan and ran with the Route Inn Hotels corporate running team. She won the 5000 metres at the Noboeka Golden Games in 2014 and was tenth over that distance at the All-Japan Corporate Track and Field Championships later that year. She ran at the 2014 and 2015 All-Japan Women's Corporate Ekiden Championships. She showed an aptitude for longer distances with third place at the 2015 Sanyo Women's Half Marathon. After a quiet 2016 she set a series of personal bests in 2017, including 1:08:04 hours for the half marathon, 8:48.27 in the 3000 metres, 14:58.82 in the 5000 m and 31:47.13 for the 10,000 metres. Her half marathon time came from a victory at the Sanyo race in Okayama and this was a new race record.