Byleth is the player character in Fire Emblem: Three Houses, the sixteenth entry in the Fire Emblem franchise. They are a mercenary-turned-teacher at the Officers Academy of the Garreg Mach Monastery in the continent of Fódlan, where they become embroiled in a conflict between three major factions. Byleth is a skilled warrior and strategist, with a mysterious power known as the Crest of Flames that grants them incredible strength in battle.
Byleth's gender and appearance can be customized by the player at the start of the game. They are voiced by both male and female voice actors in English and Japanese, respectively. Byleth is initially stoic and reserved, due in part to their upbringing as a mercenary. However, as they interact with their students and fellow faculty members at the Academy, they begin to open up and form deeper connections.
Byleth's character is able to form romantic relationships with characters of either gender, regardless of the player's chosen gender for Byleth. This is in contrast to previous Fire Emblem games, which limited same-sex relationships to specific characters. Byleth's bisexuality is not explicitly addressed within the game's story, but it is acknowledged in various supports and dialogue options.
Byleth's relationship options include several students from the Academy, such as Edelgard, Dimitri, Claude, Dorothea, Petra, Linhardt, Ingrid, and Mercedes. Each character has their own unique backstory and personality, and their relationship with Byleth can change depending on the choices the player makes throughout the game. Additionally, Byleth can form platonic relationships with other characters, such as their fellow faculty members or members of the Knights of Seiros.
Overall, Byleth is a compelling and customizable protagonist with a wide range of relationship options. Their journey through the events of Fire Emblem: Three Houses is a complex and emotionally engaging one, full of twists and turns that keep players on their toes.