Yamamoto, who won Team Kunimitsu's first title in 2018 alongside Formula 1 champion Jenson Button, has a chance of adding a second SUPER GT crown to his resume in the Honda NSX-GT he shares with Button's replacement for this season, Tadasuke Makino.
The pair are only two points away from the head of the standings, meaning a victory on Sunday would ensure a second title for Team Kunimitsu in three years.
Yamamoto told Motorsport.com: "When I saw that Raybrig is going to end its sponsorship, it's very sad news for me and Japanese motorsport fans.
"I want to win the race and earn the title for Raybrig, this is our job this weekend. Raybrig has given me extra motivation. I hope we will get extra power from them."
Yamamoto first drove a Raybrig-liveried car when he made his GT500 debut with Team Kunimitsu in 2010, but after three seasons with the team he moved across to fellow Honda team Dome. He returned in 2015 and has driven for the squad ever since.
"Raybrig is like my hero when I was young," continued Yamamoto. "The first plastic model I built was a Raybrig NSX from 1998. And 20 years later, I won the title in the actual Raybrig car. I couldn’t have imagined that.
Naoki Yamamoto（#100 RAYBRIG NSX-GT）
Photo by: Masahide Kamio
"I drove for Team Kunimitsu for nine seasons, which is the longest the team has had one driver in its history. I’ve been really happy working with Team Kunimitsu and Raybrig.
"I don’t know how it will look next year, but I’m really focused on this weekend for the title."
Yamamoto said he was also keen to ensure that Team Kunimitsu isn't the only one of Honda's three Bridgestone-shod teams that ends the season without a win.
Real Racing pair Bertrand Baguette and Koudai Tsukakoshi, who lead the standings heading into Sunday's finale, have won twice so far this season, while ARTA pair Tomoki Nojiri and Nirei Fukuzumi scored their first win of the campaign last time out at Motegi.
"The weather forecast says it’s going to be really cold on Sunday," Yamamoto said. "Saturday will be a bit warmer, so it will be difficult for everybody to choose the tyre compound.
"Honda has three cars with Bridgestone cars and the #8 [ARTA] car and the #17 [Real Racing] car have both won races. And we still have no wins, which is frustrating.
"The team has been working very hard until now, so we have confidence for this race."