The Bilibili service features something called barrage subtitles. Instead of appearing in a window to the side of a video, comments are directly overlaid onto the video itself. As you might expect, this makes it difficult to follow the action during particularly exciting parts of a video, but it does help foster a close sense of community. Of course, you can always turn these subtitles off if you find them distracting.
While Bilibili is free to use, registration is required to leave comments or upload videos. Users can also download various mobile games such as Fate/Grand Order or purchase tickets to select real-world events like concerts or exhibitions. It’s worth noting that while there is a varied selection of Japan-related content on this site, you’re required to pay in Chinese yuan. This can be confusing since both currencies are represented by the same symbol (¥).