Crunchyroll
According to Japanese tracking company Oricon, who tracks the physical releases of media in Japan, with the release of the historic 100th volume of the One Piece manga, all 100 volumes have physically sold 1 million copies according to the platform, all well as had 50 of the last 51 volumes debut at 1st place on the manga ranking charts, with only JUJUTSU KAISEN's 16th volume ranking above One Piece's 99th volume earlier this year.
Another Oricon record that One Piece currently holds is that it is the only series to have a volume debut at 1st place every year since tracking started 14 years ago, with Attack on Titan coming up second with a volume debuting at number one over 11 years.
I knew it was hugely popular but not this popular. o.O