Ryoji Mochizuki is an important character in the Persona 3 games. In Persona 3 Portable, the player character can romance Ryoji as the female protagonist. During a social link event (found here at 4:23), he states that he would still like the protagonist, no matter if they were a guy or a girl, so this leads us to categorize him as explicitly bisexual.

LGBTQ content in this game series:

Persona 2: Innocent Sin (1999): Tatsuya Suou; Jun Kurosu

Persona 3 (2006): Unnamed Female Student; Unnamed Beautiful Lady

Persona 3 Portable (2007): Elizabeth; Female Protagonist; Aigis; Mitsuru Kirjo; Ryoji Mochizuki

Persona 4 (2008): Kanji Tatsumi; Naoto Shirogane; Chie Satonaka; Yukiko Amagi; Yosuke Hanamura

Persona 5 (2016): Two Gay NPCs; Lala Escargot; Yusuke Kitagawa

See also QRM’s entry for this game series.

Citations:

1. DanaDuchy. (2015, July 22). Ryoji Social Link Romance | Persona 3. Retrieved from https://www.youtube.com/watch?v=qGEIN41WcfE