あなたを商標登録しました means “I’ve registered you as my trademark”, referring to the recent event of a vtuber registering a famous type of Touhou derivative works as a trademark.

Whew, there are quite some concepts to explain here. Let’s see..

Vtuber is short for virtual youtuber, referring to the youtubers with a virtual avatar (usually through live2d so that the avatar could mimic the posture and facial expression). The vtuber in this event is called 柚葉 (Yuzuha), who registered the trademark of ゆっくり茶番劇.

ゆっくり茶番劇 is a type of derivative works of the Touhou Project. Touhou Project is an influential project, one of the most prominent sources of dojin contents. In a typical ゆっくり茶番劇 video, chibi characters from Touhou would talk about what is happening in the video through speech synthesis.

So this vtuber registered the trademark and claimed that any creation related should pay for it, and this infuriated the community. Touhou’s phenomenal success is more or less related to the original creator ZUN’s open attitude towards copyright and derivative creation of the community. As a result, the vtuber’s company’s website has been DDoSed, the vtuber has been threatened by fans, and the law firm that processed the trademark has apologized.

And now netizens in Japan are posting jokes and memes under the tag あなたを商標登録しました to mock such exploitation of copyright, causing the tag to trend on Twitter.

The situation is still developing…

Learn more about Touhou Project on wikipedia.