The centre is set to stay with Connacht until the summer of 2025.
Aki first joined the westerners in 2014 and helped the province win the PRO12 title in 2016.
He made his Irish debut in 2017, and was a central player to Ireland's Grand Slam win back in March.
He has been nominated for this year's World Player of the Year award, alongside Irish coach Andy Farrell up for Coach of the Year gong.

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