Sounds very similar to the Mel situation, especially since he was able to make a final post on his Twitter.
July strikes again
Were there any known issues with Gamma?
Yagoo made a xeet (??) about it:
ガンマくん、今までの頑張りに感謝します。 応援頂いたファンの皆様もありがとうございました。 残念ではありますが、これまでのガンマくんの活躍を胸に刻みたいと思います。 引き続きUPROAR!!をよろしくお願いいたします。
DeepL:
Thank you, Gamma, for all your hard work to date. Thank you also to all the fans who have supported us. We are sorry for your loss, but we will keep your past successes in our hearts, Gamma-kun. We look forward to your continued support of UPROAR! Thank you very much for your continued support of UPROAR!
Gamma has a statement too but it’s an image of Japanese text so between that and linguistic nuance I don’t know how well it can be machine-translated without manual corrections.
Someone on Reddit had Gamma’s message Google Translated like this, for what it’s worth:
Regarding this contract cancellation
I would like to apologize for causing inconvenience and anxiety to all the Hololive Stars members, fans, and the management of Hololive Productions who have supported me up until now due to my lack of self-control. I would like to inform you that after consulting with the management, I received permission to post this document.
■To all Gamma assistants
The two and a half years I worked there was truly a dream-like time, and the time I spent with all my assistants was a happy and irreplaceable time.
I worked hard every day to achieve the goals we talked about with everyone, putting all my heart and soul into my activities so that I would have no regrets, and I am truly sorry that we had to part ways like this. Supported me when I was clumsy I love you all from now on and always will. Thank you very much for supporting Hisaki Gamma until now.
■To everyone who has helped me in my activities so far
I am very sorry that we had to part ways so suddenly. I was able to interact with people who I have admired since before my debut. I will never forget the memories I made with you all. I’m really thankful to you.
Hizaki Gamma
The “lack of self-control” part seems to have a vague wording in Japanese so it’s unlikely to be accurate, but the rest should be correct.
