Hiiro Amagi is a bright and energetic first-year student at Yumenosaki Academy, known for his passion and enthusiasm. He is part of the idol unit ALKALOID, where he serves as the main vocalist. Hiiro is characterized by his straightforward and honest personality, often approaching situations with sincerity and determination. Despite being new to the world of idols, his dedication and hard work quickly earn him recognition among his peers. Often seen as a beacon of positivity, Hiiro strives to overcome challenges and grow as an idol, inspired by his admiration for his older brother, Aira Amagi.