Tonga kick off their campaign against England in Sapporo on 22 September and are scheduled to play Argentina and France before their pool commitments end with a match against the USA in Higashiosaka City on 13 October.
Kefu’s side lost to both Samoa and Japan in the recent World Rugby Pacific Nations Cup, while defeat to Fiji last Saturday means Tonga have won just one of their four tests in 2019.
But that form has not dampened the former Australia number eight’s excitement as he prepares for the upcoming tournament in Japan, where Tonga are grouped in Pool C with four teams above them in the current World Rugby Men's Rankings.
“I’m fixated on making the play-offs,” Kefu said after naming his 31-man World Cup squad in Hamilton, New Zealand.
“We need to win three games for that.
“We’re in a tough pool, there’s no doubt about it. We just need to get together and believe in what we’re doing and believe that we can make it. And I certainly think we can.”
High in confidence
Tonga, who are ranked 15th, have qualified for every Rugby World Cup, bar the 1991 tournament, but have yet to progress further than the pool stage.
They did win two matches at each of the 2007 and 2011 editions, beating eventual runners-up France at the latter tournament only to miss out on a place in the last eight on bonus points.
In order to reach the quarter-finals in Japan, Tonga will likely have to win three matches in Pool C.
Kefu has included just one home-based player in his squad as he pursues that target, with the other 30 players representing clubs in New Zealand, Australia, England, France, Scotland and the USA.
Tonga wrap up their Rugby World Cup preparations with a game against the All Blacks in Hamilton on Saturday and Kefu is keen to show the improvements that have been made since the Pacific Nations Cup.
"We're confident in the way we're going at the moment," Kefu said. "Even though we had a loss last week there's some really really good stuff that we did. And we've come a long way just in the two weeks we've had since the PNC.”
Among more experienced internationals like number eight Sione Kalamafoni, half-backs Sonatane Takalua and Kurt Morath, centre and captain Siale Piutau and back-three star Telusa Veainu, there is a place for rookie prop Vunipola Fifita, who came off the bench to make his test debut against Fiji at the weekend, while uncapped Christchurch-based hooker Siua Maile gets the nod ahead of veteran Elvis Taione and could make his international debut in Japan.
Meanwhile, Kalamafoni's fellow number eight Nasi Manu has made the squad after battling back from testicular cancer.
Manu, who co-captained the Highlanders to the 2015 Super Rugby title, missed the entire PRO14 2018-19 season with Benetton Rugby while he was undergoing treatment but remarkably recovered in time to make Tonga's 31-man squad for the World Rugby Pacific Nations Cup.
A pectoral injury prevented him from playing but Kefu is clearly confident he will be fit in time to cap his inspirational comeback with an appearance in Japan.
Tonga Rugby World Cup 2019 squad:
Forwards: Siegfried ‘Fisiihoi, Vunipola Fifita, Latu ‘Talakai, Paula ‘Ngauamo, Sosefo ‘Sakalia, Siua Maile, Siua ‘Halanukonuka, Ma’afu Fia, Ben Tameifuna, Sam Lousi, Leva Fifita, Sitiveni Mafi, Sione Kalamafoni, Maama ‘Vaipulu, Fotu ‘Lokotui, Zane ‘Kapeli, Dan Faleafa, Nasi Manu.
Backs: Sonatane Takulua, Leon ‘Fukofuka, Samisoni Fisilau, Kurt Morath, James ‘Faiva, Siale Piutau, Malietoa Hingano, Nafi Tuitavake, Atieli Pakalani, David Halaifonua, Viliami Lolohea, Cooper Vuna, Telusa Veainu.