Matawalu became the fourth Roko Sau, ruler of the Lau Islands, after the death of his half-brother Rasolo, but never succeeded to the title of Tu'i Nayau.
It is said that Matawalu despised the Tongans, his sister-in-law Laufitu's people and their growing influence in Lakeba.
On succeeding Rasolo, Matawalu removed himself to self-exile on Bau Island.
Matawalu's dislike for Tongans resulted in direct conflict with his other nephew Malani, who was half-Tongan through his mother, Laufitu.
Matawalu married Siri of Waitabu and from him is descended the majority of the Koroicumu household of the Vuanirewa clan.