Some are related to Bifrost but the one I consider important is the LGBT Characters. Enomiya, of course, but also Shion Karanomori and Yayoi Kunizuka. There may be others to be added but they must be verifiable in canon or the tag will be removed.
That said, I am quite disappointed with the way the PP Committee depicted Enomiya. Not only is he a criminal, but clownish looking. In addition, it's stated that his hue clouded due to too many hormones and surgeries. The Japanese are fond of indirect/direct statements and that's one, f'sure. No more spoilers but they certainly could have done better.
Angelle