Short answers, pulled from the story.
Oricon was founded by Sōkō Koike, a former Snow Brand Milk Products promoter, in November 1967 under the name Original Confidence Inc. The company formally shortened its name to Oricon in 1992 and restructured into a holding company in 1999.
Oricon collects sales data every Monday from roughly 39,700 retail outlets across Japan. Results are ranked and announced every Tuesday, published in the magazine Oricon Style. Certain retail channels, such as 7-Eleven stores, are not covered, so the charts do not reflect all sales.
The Oricon Combined Chart launched on the 19th of December 2018 and merges CD sales, digital sales, and streaming data into a single weekly ranking. Separate Combined Albums and Combined Singles charts also began on the 24th of December 2018.
Oricon filed a lawsuit on the 17th of November 2006 against journalist Hiro Ugaya after he suggested in a Saizo magazine interview that the company manipulated its charts to benefit certain labels and management companies, including Johnny and Associates. Oricon sought 50 million yen in damages but dropped the case after a 33-month legal battle, with a settlement reached at the High Court level.
Top artists by year include B'z in 1991 and 1998, Hikaru Utada in 1999, 2002, and 2004, AKB48 in 2011, Arashi in multiple years including 2019, and BTS in 2021. Namie Amuro led in both 1996 and 2018.
The Oricon Singles Chart went official on the 4th of January 1968, after a brief experimental period that began in November 1967. It is the oldest chart the company still publishes.