The 28-year-old has been playing for Fijian Drua in Australia’s National Rugby Championship and he will head to Europe for the second time in his career.
Narumasa, who spent the 2015-16 campaign with French Top 14 outfit Agen, will link up with Connacht in the next few weeks.
The Fiji international insists he is relishing the opportunity to embark on a new challenge with the Irish province.
Naramusa said: "I am hugely excited about this latest challenge in my career. I cannot wait to get over to Ireland and start training with my new team-mates.
"The new Guinness PRO14 Championship is an exciting competition and I can't wait to line out for Connacht in the season ahead.
"Connacht has a legendary support in the Sportsground and I look forward to representing the province."