Gotogate Never Warns Me About a Required Transit Visa Before My Flight

I purchased a flight ticket through Gotogate with a connection at Osaka Kansai Airport. My reservation number/ticket number is 7819481554293; I bought the ticket on May 19th, and my flight date was May 29th. Neither at the time of purchase nor afterward was I given any information indicating that a transit visa would be required for me to complete this flight.
On May 29th, when I went to the airport to check in and board my flight, the staff on duty told me that the Chinese government did not permit it, and that I therefore couldn't be allowed to board. Despite having all the required travel documents, I was denied boarding on the grounds of a transit visa requirement. I only found out about this requirement at the airport, with very little time left before boarding.
Even though I contacted Gotogate after the incident, I received no satisfactory response regarding the hardship I experienced, and my issue was left unresolved. Gotogate is responsible for providing clear, visible, and timely information during the ticket sales and booking process about critical requirements passengers need for their travel, such as a transit visa. However, since this requirement wasn't mentioned either on the purchase page or in any confirmation email sent afterward, I was unable to complete my trip, suffered hardship at the airport, lost significant time, and faced additional expenses.
I am requesting a thorough review of the hardship I experienced, a refund of the ticket fare I paid for a flight I was unable to use under these circumstances, and compensation for the financial losses I incurred.