Seruvakula was appointed on Wednesday after Mick Byrne left the post with immediate effect following a disagreement over what Sewabu described as a "new direction" for the team heading into next year's World Cup in Australia.
The FRU said they would soon issue details of the process for finding the Australian's replacement, but Sewabu said the board had full confidence in Seruvakula to fill the role in the interim for the three matches in the UK.
"Seni's is a name that is synonymous with excellence, with discipline and the very soul of our sport," the former Fiji No.8 told a news conference after the announcement.
"He brings with him a wealth of experience that spans the domestic scene and the highest levels of international representation.
"This appointment comes at a pivotal time. We acknowledge the foundation set by the outgoing head coach Mick Byrne, who has provided a structure that allows for this seamless transition.
"The foundation has created an avenue for our top local coach to step up to the front and lead our national team."
Seruvakula has most recently been coaching Fiji's women's team but Sewabu was at pains to point out the 56-year-old knew the players very well and had led some of them to the title in the 2018 edition of Australia's National Rugby Championship.
"He has been at the very heart of development of the players who currently wear the white jersey," Sewabu added.
"There will be no adjustment period needed when it comes to understanding the character, the strengths and the aspirations of this squad."
Byrne took over as coach in 2024 after Fijian-Australian Simon Raiwalui had led the team to the quarter-finals of the 2023 World Cup.
The 67-year-old, also Australian, steered Fiji to Pacific Nations Cup titles in 2024 and 2025 as well as a first away win over Wales and a victory over Scotland in Suva.
Byrne, who has coaching experience in seven countries, spent five years working with Fijian teams, first with the Fijian Drua Super Rugby team, then with the national men's team.
He also played VFL for more than a decade with Melbourne, Hawthorn and Sydney before turning his hand to coaching.
He spent time with Scotland and New Zealand as a skills coach, before joining Michael Chieka's Wallabies staff ahead of his move to Fiji.
Radio New Zealand reported Byrne had been unwell earlier this year and his position was under review.
Fiji next play against Wales in Cardiff on July 4.
