The DLC and artbook set will be released simultaneously on May 19th

The majority of the content for the free DLC has already been completed, and it was originally planned to be released this week. However, several bugs were discovered during testing, which required fixing. Therefore, we must postpone the release date by one week to May 19th. We are very sorry for the delay and inconvenience this may cause.
In addition, we will be releasing a digital art collection on Steam on the 19th, which includes character designs and sketches. This collection provides additional content not mentioned in the game and will not affect the gameplay experience if not purchased. However, if you would like to support us, please consider making a purchase.

Lastly, we have news regarding DLsite. We are planning to release a Demo version of the game on the platform in the near future, and we will do our best to ensure that the full game is released as planned in June, as mentioned on the announcement page.