When a character's bisexuality is an Informed Attribute rather than something we ever see portrayed.
Alice is stated or implied to be bisexual, gets flirty with both genders, and/or it's confirmed by the writers, but within the story itself, all of her romantic and sexual partners are men. As one can guess, it is often the character's same-sex attraction that gets shafted, limited to only Noodle Incidents, subtext, and innuendos. This could be an attempt at appeasing Moral Guardians, especially in older works or those aimed at young viewers, but many will note the Double Standard. Sometimes, it might even go the other way if the work is aimed at queer audiences; the character may officially be bi- or pansexual in the name of inclusivity, but the story is focused on a same-sex romance.
Before adding examples, it is not this trope if a character has onscreen relations with multiple genders, but seems to be more attracted to one than the other (or they outright say they are). It's not uncommon for a bisexual to have a gender preference and only be with the other one under the right circumstances, which can range from casual sex to If It's You, It's Okay. Bisexuals in fiction and real life are not obligated to maintain a perfect gender balance of partners.
If the character has relationships with the same gender but they're portrayed as more tame than with the opposite, that would fall under But Not Too Gay, as the relationship itself is being portrayed poorly rather than the character(s). See also: No Bisexuals, Hide Your Lesbians. Related to Have I Mentioned I Am Gay?, and many of the tropes on Acceptable Feminine Goals and Traits.
