Williams made his Tokyo debut but former New Zealand All Black Steven Bates stole his thunder with two tries in a 32-22 win for Toshiba Brave Lupus.
New Zealand's heavyweight boxing champion did score his first try in the Japanese Top League but was once again on the losing side after a defeat in Sapporo earlier this month.
"It's always disappointing when you lose," Williams told reporters. "It was good to get across the try line but I was really disappointed and frustrated at the end.
"I just want to pay back my team mates and the Panasonic supporters. When we lose I feel the weight on my shoulders."
Williams left the world champion All Blacks and Waikato Chiefs for a 12-match deal worth an estimated $100,000 per game but Panasonic have yet to see much return.
Japan coach Eddie Jones and International Rugby Board chief executive Brett Gosper have both backed Williams to be a big hit in Japanese rugby.
Gosper told Reuters that Williams could have David Beckham-like effect on the game in Japan, but there still appears to be a lot to work on for Panasonic after their latest setback.
"We have to be smarter," said Williams. "We let in some soft tries and have to to the drawing board."
