Short answers, pulled from the story.
Line Corporation opened its doors on the 4th of September 2000 under the name Hangame Japan. This entity emerged as part of Hangame, an online game community site owned by South Korean NHN Corporation at that time.
The company officially changed its name to Line Corporation on the 1st of April 2013 and began trading under that title. Later that year parent company NHN split into two separate organizations named Naver Corporation and NHN Entertainment Corporation.
Line Corporation merged with Yahoo Japan on the 1st of March 2021 which had been operated by SoftBank Group subsidiary Z Holdings. Under this new arrangement Naver Corporation and SoftBank Corp each held fifty percent stakes in A Holdings Corp.
Z Holdings announced plans to merge its subsidiaries on the 2nd of February 2023 during fiscal year 2023. By October 1st of that same year Yahoo Z Entertainment and Z Data combined into a single entity named Line Yahoo Corporation.